To the girl wondering why she wasn't enough for him: Stop.
You probably did everything you possibly could have done to make things work: sacrificing every ounce of who you are to make him happy. You tried. You gave it your all, and it still wasn't enough. Every fiber in your body wanted him to be the one, but he isn't. Now you're left wondering why...wondering why you weren't enough...
Stop.
Stop asking yourself why your actions weren't enough for him or why you weren't good enough. It's not true. You are enough. Just because you were on different pages with him, doesn't mean you'll never be on the same page as someone else.
It's not the end of the book, just the end of a chapter; turn your page.
It is not your place to ask these questions. Nobody has the answer: not your family, not your friends, not him, and not you. Nobody has the answers to our break up questions because we weren't meant to understand. All you need to understand is that you put your love into someone who wasn't ready, and that is okay. The fact that he didn't feel the same way about you forever isn't something worth worrying about. It is something to relish in and be thankful you weren't stuck giving someone your 100% when they couldn't even give you 50%.
Instead of allowing yourself to drown in your own self-pity, be grateful. Be grateful he broke your heart because clearly, he was not the one. No matter how much you believed him to be or desperately wanted him to be, he wasn't.
And now you're free to accept the love you deserve.
Let him be him. Take these moments of heartache and let you be you.