Don't panic. You will only have a maximum of 2 matches per day (1 league and either cup or CL). There might not be much time between matches though, so check your fixture list.
Focus on the league. Then the CL, forget about the cup.
Have a squad with some decent subs/reserves, rotate them, rest them and use green packs wisely.
I just finished a season like that and although I was disappointed in the league, I was happy with the CL and overall season.