I often advocate people surrounding me to build their own side projects. I believe they can fulfill you in so many ways: for your career, your relationships, or your independence. Buffer, the company I currently work for, was itself a side project.
I’ve built myself multiple side projects. The major ones being PartyInBeijing (inactive), Nodablock (inactive), Citymayor (need to fix), and now TravelHustlers. I believe each of them contributed and lead me to my current situation: being satisfied in my career, financially, and socially.