1. You're an A--hole
Yup. It's often the nastiest people who fail to see that their own behavior is pushing people away from them and making them totally unlikeable to everyone they meet. If your MO is, I don't care what other people think or feel, I'm going to say and do whatever, I'm just going to do me no matter what, I don't owe the world anything, and everyone else sucks...good luck with that. When you want to be with someone, they want to know you care about them and their feelings and not only that, that you're not going to go around treating everyone else like they are a piece of dirt. If you can't get it together enough to even realize what you're doing and change your ways, you may well be forever alone because no one likes to be around an a-hole.
2. You're bitter
Being single can indeed make one bitter about a lot of things in life. You get sick of seeing other people have what you want, you're sick of being invited to yet another wedding and being sat at yet another singles table, you're tired of your parents asking you, when you're going to get a boyfriend/girlfriend or get married/have kids. It sucks, but you take that and you magnify it by turning this suckiness outward at the world. You take things very personally and become aggressively angry with the opposite sex. You start challenging why others don't want to be with you and that they should and that you're some great catch. It's a total turn off which is frightening to people you come in contact with and since people talk, you become that girl, or that guy that has the total chip on their shoulder rather then someone approachable.
3. You make no one feel special
When you get into a desperation mode, the one in which you'll just take any old person that stumbles along, and you give out your number to anyone who will have it, and you literally flirt with anybody that walks by, people get wind of this. When all the girls in your circle end up with the same guys number at the end of the night or a guy sees you flirting with all his buddies, it's unattractive and desperate. A girl or a guy wants to feel special like you want only them, but when you're just going around to everybody, you're making them feel like either you're a wanna be player or you make them feel like you're their last ditch effort 8th or 9th choice rather then first choice.
4. You're too comfortable
Dating takes effort. You send out the attraction vibes when it looks like you've showered, brushed your hair, maybe put on a little make-up and a nice outfit. If you don't give a damn about yourself and how you look, don't expect others to give a damn about you. Someone else who puts effort in is most likely looking for someone who does the same and if you can't be bothered to even try, superficial or not, you're probably not going to get anyone to notice you the way you want them to.
5. You're actually too picky
I definitely believe everyone should have standards, but some people have Mount Everest type standards for who they will "allow" to date them. If someone even veers slightly out of range of that, they want nothing to do with you. You know, they're smart, but they didn't go to Ivy league, or they love animals, but don't really like dogs, or their wonderful, but they're not the race you're used to dating. Don't just rule someone out for the first little thing. Give them a chance to surprise you.
6. You're broken
Five years ago the love of your life broke up with you and five years later it's like it just happened. No one can compare, no one is good enough, or worse, you see all the flaws in everyone else that s/he had and so for the last five years, if you can't have your ex, it's no one and you don't even realize you're projecting that on to every potential date you meet whether you say it to them or not.
7. You're in a tough financial situation
It is hard to date when you are broke. Although I believe it can be done, and I've been in situations in the past where I've had to tell someone, I just can't afford to do xyz with you because I can't, so I get this, but use it as motivation to get to where you need to be financially. People aren't always after money just because you tell them you have none. If they've been through a financial struggle in the past, they quite frankly may not want to go back to a life living paycheck to paycheck or god forbid they have dreams of what they want to do in their life, and as we know, dreams require money, so it's a hard pill to swallow but realize that even without the dating situation, if you can't even afford to take care of yourself, how are you going to share the responsibility of sharing your life with someone else.
8. You're lame
Some people have nothing going on. Literally, nothing. What do you do on the weekends...nothing. Who do you hang out with...nobody...what do you do for fun...nothing...where do you work...eh, some place that gets the bills paid. How is someone going to connect with you if you have nothing going on in your life and you don't seem to want to do anything or go anywhere or have any fun. That's like some sad old age assisted living home attitude, particularly when you're young. It's boring. Even low key people want to occasionally go out and do something exciting but if you're boring, offer nothing, don't want to do anything in life, don't seem to care about having any type of adventure, it can be a complete turn off.
9. You're over-zealous
You finally get a phone number and you text 6 times to make sure she is coming. You can't read signals from the other person that you're being too much or too extra, or you're way to touchy feely. You let him know within five minutes of meeting him that he can meet your family who would love him on your date. Give the person you're trying to chat up some space and some room to breath. Suffocating someone within 10 minutes of meeting them makes people want to run the other way.
10. You're invisible
Shy, closed off, very reserved... it is hard to get to know someone who won't even talk to you or you can't even locate because they are closed off and shut up at home where no one can find them. I mean how do you get to know someone who can't put two words together or doesn't even hang out anywhere? Very few people are going to stick around trying to struggle to start a conversation and keep it going with you for too long and that's the hard truth. If this is you and you truly believe this is hurting you most, take public speaking classes, employ a wingman, work on building your self-esteem/confidence up, step outside your head and challenge yourself to keep a conversation going even if that requires you to practice and write down questions to memorize ahead of time.
11. You need to expand your dating radius
If all you've come in contact with is people at your school or at work or in your small town, you may very well have exhausted all the possibilities of being with someone because it's no secret that certain places tend to have people with the same line of thinking when it comes to dating. You may not be what's attractive in place a, or they may not like your religion there, or they may only like people who have certain backgrounds which you don't have, so try somewhere else. Go to a bar somewhere else. Go on vacation and try flirting there. Go online. If all you hear is no in your current situation, branch out and expand your dating radius to an entirely new population.
12. You believe yourself incapable of being in a relationship because...
You believe you're too ugly...too stupid...not fit enough...not funny enough...not dateable enough...not on and on, enough. If you start to buy into that method of thinking, you will defeat yourself before you even try. You do actually need to believe yourself worthy of love. If you don't believe it, how will they?