I don't know how long you were in the relationship or how long ago you broke up?
Please do allow yourself time to feel your hurt and distress as the ending of a close physical relationship can be as real and as painful as physical trauma. Sometimes that is made all the worse if you don't see it coming. Sometimes there are warning signs that all is not well., but regardless a break up is horrible, painful and nasty. There is usually an 'injured' party. The one side of the party being 'abandoned'
It is difficult to see anything positive when your pain is so raw. But if either of you are believing that the relationship is 'not for you' then it is probably better for it to have finished sooner rather than later. There is nothing wrong with you, other than you were both just not a perfect match. They were as they were, you were as you were.
The best and most enduring relationships are those where each person complements the other. A yin and a yang. The best relationships are where you can be yourself absolutely; where you don't have to change or do anything differently. That someone will love you for who you are, and not try to change you. You will love them on the same unconditional basis. Never ever fall into the trap that 'I should have done ...." I should have been ...... 'thinner, fatter, more athletic, more refined, more sociable' etc etc etc Quite simply you are as you are. If you weren't good enough for your partner well tough. That is their loss, not yours. Don't fight it, don't grovel or go back and plead. If they have changed their mind, or fallen out of love then get out of that relationship and stay out. If you go back the hurt will only repeat itself again further down the line and you will be burnt for a second time, a third time, etc etc. You need to be resolute. You believe in yourself - trust your judgement but don't get sucked backwards because you try to be someone or something you are not just to please them?
Find some good friends and ask them 'why they are your good friends?' Then believe them. Take a breathing space. Look at the person who is giving you a hard time? They will do that again to someone else - so heed the warning and leave them alone. Yes it hurts but in the long run you will be better off. Do all the things you can do to 'love yourself' and to nurture and sooth your hurting soul. Once you realise you don't need someone like them to make you happy you will be a more confident person, and a happier person less reliant on someone else's opinions. Sod them. Be your own boss, get out there, have a good time and don't look back. This person does not deserve you at all. Put all of your energy into feeling better and doing absolutely everything you possibly can with everybody else but without them. Force yourself to find people who are happy and funny. Never look back.