@Trance:
just..
- if your team has equal or better matchup advantage
---- be bothered if you or your team missed a chance to win (or even if you win but could've avoided some critical mistakes), don't be bothered if you, and everyone else (from both teams) have pushed themselves well enough :p
- else (matchup disadvantage)
---- stop caring

(this may be difficult if you don't foresee the teams' potentials -- escape options, effectiveness of front line characters, pushing ability, stuns/disables/heals for controlling the flow of teamfights, harass at early game, etc.)
maybe you
didn't have enough chances to employ your playstyle effectively (surely, people around here are getting familiarised with who thinks with
portals the allies or not). Maybe an important element (imho) is being overlooked, which is.. team character selection (sometimes I screw myself because the character I meant to pick was meant to support someone else from my team, but then said person -- not exactly you the last time we played, but other examples which were more synergic imho -- switches the character, making it hard for me to try to foresee how to make our gameplay safer), and trying to create a team strategy and/or frustrate the opponent team's.
I know you've said once that if you had to think about character selection, you'd rather play DotA instead, but for me, thinking about strategies and making lots of decisions through the game is what makes this (and other games) fun for me. It may be that DotA is more flexible, regarding individual characters' matchups (less cases of a character having too much advantage/disadvantage against another), favoring both team strategy and individual/small team battles.