You're Sombra.
It's the beginning of a new payload round, this time on defense. Your team remarks that the enemies won by fighting very hard last round and will probably push very hard again. Your team asks you to switch off of Sombra this round since she's unreliable on defense, due to having neither the endurance nor the damage output to hold off enemies for a long time. You refuse to switch. The enemies steamroll your team in this round too, winning the match.

What went wrong?