On the margin I think its usually better to take less and/or easier courses. It is better to do very well on an easier schedule than do "ok" on a hard schedule.

I was uncertain, coming from high school to university, whether or not I would adjust well. So I did the cautious thing and hedged: I only took 12 credit hours (the minimum load) the first semester.

About three weeks in I was talking to one of my professors, complaining that I was bored out of my mind. They offered me a research position in their lab, and getting involved in student research my first semester was much more helpful than a class would have been. Similarly, if you find yourself with spare time and energy, find a productive outlet for it. Get used to building in pad time for yourself and then using that pad time flexibly. (This is a key factor in avoiding burnout during your adult life, I think.)