How to encourage teammates?

I won't lie, I've been that guy to silently blame teammates for ranked losses. Its not often I outright jump in the game and trash talk my entire team because of whats going on. I don't do it often because I can't even count the number of times where epic comebacks happened. You just have to play the whole game out, it can be stressful but miracles happen in this game ALLLLL THE TIME.

How can you encourage teammates to stop giving up so easily, trashing teammates and afking? I know the common tip is.."its not the team, its you." right? But when you have teammates who are throwing a fit and disconnecting it CAN'T just be my fault for this happening. Recently, I try to tell teammates like hey..its not over, don't give up, and when I'm upset myself I can't be abrasive( not often but it happens, this is League). I'll tell a teammate look, STFU the game isn't over at 15 damn minutes yknow? It just sucks because some players really take these losses to heart and start attacking teammates morally and thats what ultimately lessens morale and rather than be a part of the toxicity, I just want to encourage sticking with the game.