Some people take it well, others not so much. My parents tend to be super chill and are handling retirement very well, my dad can't sit still (tries to do DIY stuff he shouldn't be doing at his age) but he's always been that way.

My in-laws are both just about retired, they are rapidly losing their minds because all they've ever known for the past 35 years is work or taking care of their 4 kids and now they have neither. My FIL doesn't understand how to not be working, he will literally go home to do yardwork in the middle of vacation because he can't take it anymore. All my MIL does is complain about how much he irritates her. Both of them need hobbies and fast.

I feel so grateful that neither of my parents ever got into social media

If you don’t stay busy or in touch with your friends, you’ll just fall into a hole and post crazy shit online to get attention

Terry Pratchett had a good take on this in his book "Men at Arms". "Individuals aren't naturally paid-up members of the human race, except biologically. They need to be bounced around by the Brownian motion of society, which is a mechanism by which human beings constantly remind one another that they are...well...human beings."