Turned 40 too recently.

I have a much more relaxed feeling than I had 2~3 years ago. I am content, even happy, with the life choices I made. My family and I moved from Europe to South Africa, and while that has made the work side harder, the life side is so much better. Kids love it. They go to a much better school. We live outdoors most of the year. We hike. We sport. I took on surfing.

Like others have mentioned: reach out to those friends. Just a "Hi, how are you? I was just thinking about you and wanted to hear how you've been" can be the simple ice-breaker.

You're about at the half-way point for your life: what gives you joy? (playtime with the kids? learning a new hobby? ...?) do more of that! What gives you anxiety? (work? new boss?) figure out if you really need to spend time on that.

There are a thousand books about these things, but it's not really rocket science. Accept who you are. Accept who other people are. Make changes if you want.