Most of what you do should feel easy.
If it's not, you're taking on too much. Either your task is too big or you're moving too fast.
Break it down.
Breaking things down is a challenge in itself. It forces you to think critically about what you're doing - looking for the main ideas, sorting priorities. If you make that the hardest part, actually carrying out the tasks won't be such a headache.
This has immediate application if you're learning a piece of music. I'm trying to keep it in mind as I set about writing a book.
Where will it help you most to slow down and break it down?