The actual answer for me is that it's just how I paint. In fact, when I have to paint tight and detailed I feel like someone is strangling me. And I hate when that happens. So here's 4 approaches that will help you to loosen up when you paint. Try one or more and let me know if it helps!
- use a large brush or palette knife (emphasis on LARGE)
- paint using your non-dominant hand
- have a drink (or do something to take the edge off :) After all, it's paint and canvas. There'll likely be many others so don't worry so much. The painting police won't arrest you if you mess it up.
- stop at 90%. This tip is actually something that my colleague Bob Burridge recommends, so I can't take credit for this one. Bob also teaches some wonderful workshops to help you loosen up (click the link for more info).