The biggest mistake I see most travelers make is planning too many activities. Leave gaps in your itinerary so you can add stuff you learn about after you get there. You may have days where you don't want to do as much and you would rather relax. By leaving gaps, you allow yourself to slow down and enjoy yourself while still having the option of doing more.
For those of us who are autistic, HSP, introverted, or have sensory processing disorder, you may want to plan for whole days off occasionally. I tend to stay in the same place for 1-3 months to really get to know a place and every 3-4 days I spend a day resting, reading, and/or binge watching a show on Netflix so I don't get burned out and have a bad time. If you only have a week in one place, maybe you don't want to take a whole day off. You can still allow yourself the day of arrival to just get settled in, with no activities, and take half a day off mid-week if necessary. So many people say, "but I'm only going to be here once. I have to see everything!" I say, "I'm only going to be here once. I want it to be a good memory."