Most Helpful Guy
You know you love them if he makes you smile and you enjoy having his company and you never seem to lose that feeling of enjoying him being around after a few years of dating. Also he'd have to be polite to you and try and do nice things or be romantic cause he wants to woo you over. If you two ever got into an argument, you both would have to be willin to forgive each other and not let a bad day or some silly excuse get in the way.
You'd have butterflies long after you two have been dating and long to spend time with each other. Nothing would seem to lose its touch and you'd appreciate everything he and you did for each other.
Finally you need trust. Not just with if he is cheating, but to be honest with each other and not let jealousy or problems cloud your mind. You need to be able to easily discuss things with your partner rather than bottling it up cause you think the truth won't be too great for them to hear.
Yes I'm only 18 but the key words of Love is Time, Truth, and Hearts :) basically the feeling that he is the one seems to never fade or go astray. However some people don't wait long enough and get married like 2 or 3 years after dating :\0THIS IS NOT RELEVANT ANYMORE