I had a boyfriend for 3 years, I have never met someone that I am so similar to ever.. when we talk it just feels perfect, like he knows me better than anyone in every way. When we were together we had problems but looking back we both loved each other but were just insecure and couldn't just realise that.. which led us to take things for granted. We broke up after 3 years and ever since I have realised how perfect he really was for me.. we could have been together forever if we just realised at the time! I love him more than anything but I feel like for him it's too late, like he doesn't want to go back there. I feel like I have grown up and we could be perfect together this time but I don't know how to make him want to go back there again when he feels like we have failed! We could be so happy this time.. what do I do?

“Sorry" doesn't work every time. Move forward.

I notice that you gave advice to someone else, saying she had to 'make him' realize. You can't 'make' anyone realize anything they have already turned down. Your boyfriend is done, over, final. In rare cases people come back after some more failures, but it's VERY rare, and you just have to accept it.
Send him a birthday card once a year, and leave it at that. Maybe in 5 or 10 years, who knows.

It's not really a case of sorry, we both realise now our problems and that it was just a case of us not realising what we had at the time! We both know we could have been together and with us.. everything feels perfect! I just want him to want to try again when we have both realised everything

You say he's done, final.. but he tells me that he will never love anyone like he loves me etc.. doesn't sound like he's really done to me! And by make him realise I mean don't give up.. she needs him to see she she has changed! Obviously she can't force him, figure of speech you know