On failures and mistakes
Failures and mistakes are great fun, but they should not be your only option.
Improv embraces failure and mistakes like nothing else does. At improv workshops we regularly encourage each other to take risks, enjoy fear and fail good-naturedly.
However, you need to commit and try hard to reach an honest failure. Even more so, succeeding should be within the range of possibilities.
So, aim high and far, but don't set ridiculous goals either. Nobody enjoys watching you fail to jump three metres high, but watching a person who can't really sing commit to a love song can be awesome.