Retired & Lonely, I feel it too
It's sad yet comforting to know that I'm not the only one who thought he wanted to retire more than anything in the world and realizes, 1-1/2 years and counting later, that it was a terrible mistake.
I try to keep busy and try to stay "positive" and put on a happy face, but the truth is I'm lost without an inner sense of purpose or contentment and realize that I walked away when my skills were at their peak. I retired because I thought I was suffering from job-related stress and anxiety but after retiring my stress and anxiety became worse and work had actually mitigated the symptoms, sigh.
There's no do overs and life has to go forward. I'm doing the best I can but have unfortunately have lost my enthusiasm for life, which just isn't my personality, at least the old me. I'm able to fake it that all is well though and I'll keep working on it.
Nobody ever warns you about the emotional consequences and fallout of retirement, only financial.