Usually I have like 60 things to do on my to-do list in a day. Some are small and take few minutes, some are big and can take few hours.
It was hard for me to drop stuff for a long time and I just carried it over and tried to catch up later, which, as you can imagine, can be quite stressful.
Now, I tend to drop stuff not achievable during the day if the priority and reasoning for it does not justify rescheduling it.
Without having clear Why and priority, it would be impossible to do.
Do the tasks on your to-do list have why and a priority?