Should I give up?

[P.Petrov]

Mate, as I understand the game engine, GK has absolutely no impact over the action, exept if he saves some 100% goal from time to time. Maybe you went attacking and your opponent was defensive and his team used his chances. It is also possible that your team had bad luck day, it happens all the time. I think you should try with some balanced(not attacking approach) next game and patiently wait to see if it is going to be your day in the second game. I dont see a reason to save 15% condition for your startiing 11, because you have small chances but imagine if it is your day and you win 4-1 Also you should know that even your next game is 10 min after and your players are 85%- that is not a big issue Good luck

[Altiplano]

I once lost the 1st leg of a cup match 0-5 at home. I was so hacked off with my players that for the 2nd leg I swapped them all out. Started with players who were normally subs and reserves. Won 6-0 away. Qualified for the next round. This was more than 12 seasons ago though so the game mechanics might have changed, but you never know.
Good luck.