I tend to overschedule and overtask myself on Mondays.
At the beginning of each week I have a huge list of to-dos, and I normally underestimate how long each thing will take. I try to tackle these things straight out of the gate on Monday. I end up finishing about 1/3 of my list, which makes me feel frustrated and I wonder where my time went all day.
Another aspect of this problem is procrastination. Those tasks that didn't get completed last week have now moved up the urgency ladder and I have even more pressure to complete them today.
Do you tend to overtask yourself on Mondays?