When you leave the labour market, you get the time to resume some of your old interest or find new ones. Pursuing your interests together with others is a good way to stay active.
If you reach out, you can find networks for just about anything you can imagine. For example, sports, winter swimming, museums, travelling and gymnastics. Most likely, you have your own interests, and now is the time to really start pursuing them.
If you would like to make a difference for others, you might consider becoming a volunteer. Many associations and organisations need more hands, and it is up to you how involved you would like to get.