I actually disagree with the above.
My hand skills were not good and they only came with time and practice, but I never went out of my way to improve until working with patients. I had no idea what I was doing in pre clinic, especially crowns. If I spent more time studying why what I was drilling was important, such as the importance of reducing X amount of mm in each area to accommodate the final restoration, I would have probably not been as frustrated with dentistry during pre clinic.
Frustration will be plenty throughout school. Just remember that every experience you have with patients is a learning experience. Every class you took that you thought was dumb (prosth and dental materials for me) actually serve of great importance. It isn't as clear cut as saying "I wish I could go back and do XYZ" as at the time it didn't seem important because we had a ton of other high pressure exams going on; If I didn't go great on those exams I would not have made it to my fiercely competitive GPR program.
Now more than ever I find myself trying to learn about topics we studied long ago in the past. This isn't a bad thing, this is dentistry. Many dentists don't do this. How do I know? D4's are mere months away from becoming practicing dentists and if people aren't going above and beyond now, they certainly will not change in the future.
Don't expect to change this overnight. It will be a slow transition. You will make mistakes. You will pulp out. You will spend 3 hours on a class 1 restoration just as I had that can now take me 20 minutes. The most important is the culmination of every little small fact you learn across your career and incorporate that into daily practice
I also recommend becoming intimately familiar with dental materials, especially composites and cements. Don't memorize everything, just know the standard protocol for use.