You are not a failure. The marriage ran its course, that's it. Very sad and disruptive, but no indication of failure. By 50, you must have suffered some bereavements ... they aren't 'failures', are they? Like any other bereavement, this one (your marriage, retirement plans, etc) needs grieving. Allow that.
Sort out the finances, homes and other practical arrangements.
Learn to be selfish. This is, now, time for you. Indulge your emotions - grieve in 2-hour baths if you like, get yourself a lovely soft blanket to comfort you on the sofa, take your time.
Remember the things you used to love doing - old hobbies, creative pursuits, sports and games, clothes shopping, everything - and give them all a run, to see what you love now. Then try out some new things.
DON'T look for a replacement man to fill the hole you seem to have in your life. Make your OWN life complete first; Mr2 will turn up in time if that's on the cards. DO get back in touch with old friends, even if they're from way back. We've all had bumpy lives, you know, we're very tolerant of re-appearing names and complicated life stories now!
Remember to eat properly :)