1. It really is too soon
If you really liked your ex, and you dated for a long time, and you're wondering why a month later, you haven't moved on yet, it might literally be too soon. You can't force yourself to just be done and over with someone right away, especially someone you shared a life with. It requires a bit of a mental shake-up, it may require you to get mad, to scream, to cry, to punch a pillow, to do some soul searching, and a lot of letting go of what you two had together, none of which you can just run from, because when you do, it's all running there right along with you no matter where you go to try to escape the feelings. You have to allow the process to unfold and to quite literally grieve your loss. Conversely, friends will do what friends do which is trying to get you back out, and back on your feet, and to help find your happiness again, but if you're still hurting, you can't change that on their time line because they aren't the ones who dated your ex, you did.
2. Hindsight Fantasy
You know when someone dies, and people talk about them at the funeral as if they were practically saints; that can be a lot of what happens in a break up. Despite how it happened, you can sometimes start to paint this incredible picture of how perfect your ex was. They never did anything or said anything wrong, they were the nicest, kindest person, etc. but it's easy to forget in this foggy cloud of memory and regret, why you broke up and how you got there. Most people don't just break up because a relationship was prefect. You need to know and begin to understand the reasons you are where you are, and not put your ex on a pedal stool. Friends can and do often let you know that what you think you remember and what actually happened where a lot different. You just have to allow yourself to clear the fog so you can see that too.
3. They've Moved On
If an ex moves on and you can't or haven't, it can be hard because you sometimes want to compare yourself to the new person. What have they got, that you don't? You're so much better than the new person, so why can't s/he be with you instead? This new person isn't right for him/her, but you are. How can your ex possibly be happy without you? And you might be right or maybe just edging on to crazy town, but when you broke up, you no longer have a say in what your ex does or doesn't do because they aren't in a relationship with you anymore. What they do is their business. It's natural to feel hurt or to want to compare, but if you go down that rabbit hole for too long, you'll spend your days so focused on what doesn't exist anymore or perhaps isn't even true, and you'll begin to miss out on starting to recover and move on in your own life.
4. You Haven't Forgiven Yourself
If you cheated on your partner, or you weren't as involved in the relationship as you could have been, or you were constantly disrespectful of your partner, or for whatever the reason you broke up, and you know that it was your fault you ended up where you are now, a major part of your recovery plan should be to take the lessons of your failed relationship and work on ways not to do the same thing again. You have to be able to forgive yourself for the person you were with them, and work on being a better person for the next person. Even if you managed to apologize for your past indiscretions, it doesn't mean your ex should or has to take you back or should even except your apology, but in some cases, moving on could mean you need to accept your own failings for yourself and grow to be a person worthy of a new and better relationship, so you can move on and stop trying to fix what you already broke. Somethings just cannot be salvaged.
5. Maybe you really do need to get laid
Yeah, sometimes you need some sexy time to shake loose the memories of the ex. If all you can do is picture his body, and everything she did with you, and you have no other vision of something to replace it with, getting laid can actually help. I would strongly advise you don't try to turn your first go round into anything serious until you've officially given yourself more time to heal on a deeper level, but a little fun, can be just the thing to turn things around for you so you can start thinking in more positive directions.
6. You're still pretending nothing has changed
Is your house, apartment, or bedroom still littered with the memories of your ex? Do you still go over to their parents house for Sunday Dinner or hang with his or her friends more often than your own? Have you refused to tell anyone you're no longer together, especially months later? Change is super hard as is being able to let go, but the fond memories you have are still saved up in your mind. You don't need to have constant daily reminders of what could have been in physical form, especially if it is really really REALLY over. Have a friend help you de-boyfriend or de-girlfriend your place. You may be tempted to hold on to things, but sometimes its easier if someone else dumps it all in box and gets rid of it for you in a great cleanse. It may still be painful and it may still hurt, but use this time to replace those items that reminded you of your partner, with new things that bring you new joy and happiness. Take their picture down and replace it with a picture of your dog or your best friend.
7. You're allowing your ex to play games
One minute you're breaking up and the next they are texting you wanting to get back together. You replay this game over and over and over again, each time thinking, this time will be different, but yet, here you are in the same exact position where you're pissed, and angry, but still grasping on to hope that they will change...this time. End this cycle because it only keeps you down, keeps you running back into danger, and keeps you from being able to fully move on. It isn't your sort of ex who needs to change here because you know who she or he is by now and what they're going to do...it's you who needs to grow up and move on to a steady and stable relationship or a life where you are working on making you happy. If you can't see it, pull up those old emails and texts and look at the vicious pattern of faux apologies, lies, and struggles you've been through just by trying to be together. A relationship is hard, but it should never be that hard.
8. There is nothing going on in your life
If your whole entire life was consumed by where you and you ex hung out, going to stuff they liked, or doing the same routine all the time, yeah, it may literally be a case of, what do I do without them. If you feel you have nothing to fill the hours of your day or your weekends anymore without spending time with them, you need to find new hobbies, new hangouts, work out, go back to school, re-connect with your friends and work on developing your own life. You are NOT helpless without your ex. I repeat...you are NOT helpless without your ex!