I've been around enough mental illness to appreciate that there is only so much anyone can do--at least not without engaging in codependent behavior.
Takes real wisdom to recognize that. You gave him a great friend and riding buddy and that's all anyone can really ask for. Hugs to you and be well. as the others said, think about the good times and the positive presence his life was to you.
Sarah
When it's easy, ride hard; when it's hard, ride easy.
2011 Volagi Liscio
2010 Pegoretti Love #3 "Manovelo"
2011 Mercian Vincitore Special
2003 Eddy Merckx Team SC - stolen
2001 Colnago Ovalmaster Stars and Stripes