When I first started, my instructor could tell if I was stressed out from the night before, had a bad day at work etc so I resolved never to fly after work again and never fly if I had a busy evening planned the night before.
I was most relaxed when my lesson was around 10 am as it meant I had time to get up, have brekkies and get to the airfield without having to rush but didnt give me time to start thinking about what the day would be like, what if this happened, etc etc...
Perhaps you are trying too hard at the minute and your problems (as you see them) are made worse by worrying about things beforehand.
Sometimes a longer break between lessons can help, ie, take a fortnight off then resume.