Definitely my current endeavor, bastions [0]. It's the first side project that I've taken this far and I can't wait to see where I can take it from here. In a sentence, bastions allows website owners to easily and automatically test their website. Think testing out contact forms, sales forms, SSL certificates, functionality, etc, in just a few minutes time. It's been rewarding because I've done it all myself and have learned a lot along the way.
I say go for it when it comes to starting your own thing. It's hard, but it's rewarding.