I am turning 35 years soon and I feel like I haven't achieved much, both personally and professionally. I have held jobs in small and big companies for mostly for 1-2 years each, traveled and lived in different countries, had 2 failed startups, and have about $500k in savings. I am single and haven't had a serious relationship for many years now.
As time went on, I started feeling less excited about everything, personal or work related. I used to be excited about new technologies, but not these days. I feel like I've seen most things before, and it's all just different iterations of the same. I increasingly wish I could go back to my 20s. Now I feel too old to go to festivals, bars and clubs and make new friends that way.
This has been a recent change for me. When I was ~30 I still considered myself young and able to do anything I could do when I was in my 20s. But not anymore now. I feel like my time for everything is running out. Have you been through a similar thing? How did you deal with it?
The problem is that by 35 you can't get by on novelty anymore because you've seen some version of everything there is to see.
The worst thing you can do is pine for the good old days. They aren't coming back. And they weren't that good anyway. Your best times are ahead if you can successfully adjust.
What worked for me was putting down roots. I resisted it mightily at first because I wanted to stay mentally 25 forever. Now I see that getting married and having a couple of kids was the right thing to do. It forced me to become more flexible, more deliberate, more focused and have more stamina to do hard things
I'm a loner by nature, so I can't imagine where I'd be if I hadn't settled down. I just know it wouldn't be as good.
Once you've got those roots down, life will lead you to what you should do next. Maybe being a full time parent, maybe learning to sail, maybe more successful entrepreneurship. Who knows...
EDIT: I don't mean to imply that everyone needs a family. What's important is to start living for others to some degree. Hedonism has famously bad diminishing returns.
Some people choose to do lots of volunteering or switch careers to social work. There's lots of options.