[lettfly]

You will probably never know why but it should not matter.

His walking away is surely devastating and the emotional pain on the mental psyche can tear at you from the inside out, outside in and all over again. Nip it in the bud.

Acknowledge what he has done, come to terms with it, grief it even be angry about it but tell yourself you are a better person w/o your bf. You have to be, you have other people who care for you, your parents for example, your siblings if any and surely you have friends who will stand by you no matter what happens.
If you are lacking friends or have this doubt that makes you wonder if you still have friends maybe it's because you have spent your lives being too much involved with each other and as such neglected your friends, in that case, call out to them for support. Those that care for you will be there for you. Else, make new friends! As the Irish like to think, A stranger is only a friend you have not met.
The money lost can be earned back. Sure, it takes time but still it will be back. What you cannot lose is yourself, once you lose yourself you lose everything! Live your live better than you have ever before. Be a better child of your parents, a better sibling, a better professional at work and a better friend. cut out the emotional and mental anguish that can only slow you down.
Last and surely not least, wise up from this experience, take the pain as a battle scar. Remember of this episode but do not let it colour your life. Open your eyes to a better someone. Someone who would love and care for you for what you are worth and whom you can trust to put your head on his shoulders when you are down. I hope for your own sake you embark on a better adventure hereon and never look back.