Just because you probably made some mistakes in this relationship doesn't mean you're ruined. You have to forgive yourself for whatever happened that you feel is your fault. Perhaps its the best thing for you right now not being with him. This will give you time to reflect on your relationship- what you've learned from it and how to apply it to your future relationships. Get to know your self better and think about what you want out of life. You should be able to be happy by yourself before you can be happy with anyone else, especially for a lifetime commitment of marriage. The worse thing you could do is get married while pretending everything's okay when it isn't. This will definitely lead to an unhappy marriage. If the person loves you, he will forgive you. But before you can work it out with him you have to work it out with yourself. I'm not sure this advice will help you much since I don't know much details of what happened. But I hope you are able to gain something from it. Have hope, love yourself. You will be okay. Life is still here. You are still young! Smile and stay strong!

i am also your age and i went through the exact same thing just recently with my best friend who knew how i felt. i said something stupid and unfounded that cannot be anything but forgiven by this other person. and yes i've never felt stronger about anyone before or more of a mental match, nor have i ever loved anyone that deeply before despite problems, communication, background and whatever else, not ever. it's been over for two months and i'm sure she's moved on, but i'm still kept up nights over it. buy i decided to arm myself with knowledge--researching and asking all my friends and experienced people within my locale so that i'd never hurt anyone thoughtlessly again or be a villain when peace is what we were both looking for. i eventually ended up researching true love, in biblical and buddhist teachings. both entries give close definitions of what true love is, but the buddhist teaching goes further and says that you can't love anyone else unless you know how to love yourself. and you can't love yourself unless you know how to listen to yourself. that means you can't love them until you really know how to listen to yourself, and then them. not just by words but by interpreting your own feelings and actions. sometimes people don't know why they feel certain ways and they say the wrong thing. but learning to listen to yourself can tell you what was wrong. maybe you weren't completely happy and sabotaged the relationship. maybe you had trust issues... it goes on and on, but love means being able make someone else happy, take away someones pain, willingness to make them happy daily, and willingness to uphold their freedom (not keeping them in a box with jealousy, insecurity, etc). couple that with the understanding that life in and of itself is transient. so getting the fact that things are temporary, and that people's feelings can change overtime, and you start to understand that the concept of "the one" isn't all they make it out to be. that doesn't mean you loved that person any less, but that means that if it didn't work out, there's not a tear in the fabric of destiny. imagine if you had kids and it didn't work out. then you'd have years of pain before it got better. and guess what, you don't have to love that person any less than you might right now, but if it's true love, then you can accept the fact that romantic love can't happen right now with that person and may never happen and still love them without tearing yourself down at night only to drag yourself to work the next day wearing sunglasses. but never think that other person completes you. if you do, then that means you don't know how to love yourself. that other person may have some great qualities. but guess what? those qualities you see in that other person are already within you, which is why you may have admired them so much, and felt suited for them. no one's saying tape on a mustache and act like your ex, but you should definitely develop yourself to become a whole person, to love and nurture yourself to that point. once you're out from under the shadow of that deep love you felt, you'll really be able to see all the good in that old situation and benefit from it in the present. i've said too much, but what i really want to endure is the fact that crisis produces change, and if you're going to change anyway, i'd rather you changed for the betterment of yourself and everyone around you than get anchored down with more baggage and regret only to wait a couple more years and this happens again.

Give yourself time to grieve. It also mightn't have been as much your fault as you think. Sometimes relationships bust up and it's just rotten luck.