My sister was widowed over 30 years ago when she was in her 50s. She was still working at the time, which she has since said probably saved her emotionally in a lot of ways.
Over the years after she retired, she had a few casual relationships with men and one serious one. Well, it turned out she was more serious about the relationship than he was when it came down to it, so she broke that off.
Now that she's in her 80s, she has found happiness with a man she met at her church a few years ago. It started as a friendship and progressed slowly into a deeper relationship. They aren't married and neither want to be. Nor are they living together, which neither want either. But my sister is a social person (which I am not) and she has someone to do things with. She did help to nurse him through a serious heart surgery, but only because his kids don't live close to him. They have a great relationship but also respect each other's lives outside that relationship. It works well for them.