Venting is not my recommended solution. Venting just predisposes a person to act out their anger.
Learning to not let little things get to you is about practice. Sometimes you succeed, sometimes you may not. Getting angry really doesn’t help anything. It certainly doesn’t help you.
That’s not to say that if we do any certain particular thing that nothing will ever anger us again, but learning to let it go and understanding the relative importance of transgressions against you will help you deal with those situations calmly.
People who do nasty things to us, are doing so because they have a problem and they’re trying to project their problems on to others. We don’t have to let others’ problems become our problems.
Lastly, let the little stuff slide. Most of the stuff, is little stiff.