I’m deeply sorry that you’ve lost one of the many treasures in life - I truly know how it feels. I’m hoping it isn’t an actual passing, considering not too long ago I’ve have just lost a friend, but comparing that to a true friend that’s there for you everyday, that’s there to talk to, and that’s there to see if every thing’s going alright, I can’t imagine the loss of such remedies, regardless of how loss can be defined.
Why are you blaming yourself, exactly? If you’d like to expand about that reason as to why, please do - you mentioned something about your guys’ relationship, so I’m assuming that something must’ve happened in between those times, influencing his separation from you.
I’m really sorry about your best friend. It can feel hopeless without that kind of spark in your life, throughout your days. But if you need to find a way to cope through it, I can tell you that if you can find the forgiveness within yourself, whatever the reason is in blaming yourself, you will feel much better about confronting the situation in a more clear, less stressed atmosphere. If you’d still like to DM me about this deeper, please do 
◞ 🎶 If words fail, music speaks! 🎶