One common thing that tilts me
When your team wins a fight or takes the baron or does the sneaky split push or whatever and manages to take an inhib, that's great! It's actually, factually, truly excellent. Taking inhibs secures victories like nothing else.
What tilts me to hell and back is when my team takes that first inhib and then sticks around. You've already taken the most important objective that you can there! No, nexus turrets aren't important. If we're winning, they'll fall anyways. Don't fuck around trying to fight the enemy team in their base or grab random CS! Take the inhib, back out, and rotate elsewhere! Don't give the enemy team a chance to assault you with everyone fresh while we're all low on health or mana!
Just. Fucking. MOVE!