Protip: Don't feed, then harass your teammates. (Don't harass period)

It's okay to have a bad game. We all end up feeding (UNINTENTIONALLY) at some point. It happens. But if you end up tilted because you lost lane, got camped, misplayed, etc, DON'T start flaming your team. Ask them for help if needed. Tell them what you need to come back, fine. But no harassment.

Think about this. You have a bad lane matchup, enemy jungle camps you. You die 3 times in 11 minutes and start to play safer. But you're tilted. Or you're jungle, and get invaded early and give up first blood. You plan your paths and ganks carefully knowing you're behind. Something goes wrong, someone else messes up a little bit, YOU die, and you start flaming them. But you're the one dying. Suck up the rage and keep going. You can win from behind.

But if you're negative and/or tilted, harassing will tilt you more and tilt your team. You're already a little bit in the grave, and you're digging yourself deeper. Don't do it.