IF YOU DON'T EXPECT TO WIN, YOU WILL NOT WIN.

A team fight in my last game exemplified this PERFECTLY.

I was Katarina, and initiated on to the opponent's Elise, Caitlyn and Lux, despite the fact my team overall was very behind (Bot and Jungle were feeding). This is because I knew I had enough damage to at least kill Lux who had Mejai with 20 stacks.

Going in solo, I succeeded in killing Lux and put Cait and Elise down to extremely low health. My team's Thresh and Riven were right behind me. Riven flamed me for going in, saying it was "dumb".

They were both full health. Alone, I got the opponents really low, but Riven just expected so much to lose she refused to fight, even though we were up against the opponent's squishes and we both had superior AoE damage. We could have gotten three free kills.

But my team was so set on losing because "GG feeders" they didn't even try to abuse opportunities even when handed to them and so, well, we did lose.

Meh.

But, yeah. If you expect to lose in-game, in-fight, etc. you WILL lose even if just because you are not looking for opportunities to win.