I'm a bit late to respond, but nevertheless.
Backstory: 4 of us joined to make a product. 2 of the 4 people had the idea and invited me and another guy to join them in making it happen. All cool.
Except that I didn't quite like one of the 2 'idea' founders. Objectively he's a great potential business partner, has a ton of ideas etc - a hustler type, but he has some character traits that really get on my nerves.
Ex. tyrannic way of suggesting changes + all of the decisions eventually have to go his way. You can fight it, but it drains so. much. energy. Micromanaging tyrant would be a good summary.
Anyhow, I knew this but still went in after disclosing my concerns to the other 'idea' founder. I was confident that I will find a way to work with him, and actually made a challenge to myself to at least use the situation and learn how to handle that kind of people. But long story short, eventually the friction made the partnership too uncomfortable + the product failed (technically his fault in the marketing department), so naturally our contact dissolved away.
I still think I could handle our conflicts (while coding the product) in a better way, but ultimately the biggest benefit I got out of the whole ordeal was honing my bullshit alarms and detectors. Also improving in saying no, but that's still quite a long way from where I'd like it to be.