Something I didn't do at first but did soon after getting my PPL and wish I had done it sooner was to go and safely test my comforts and limits.
It's quite possible that others won't agree but after my first few "I'm a real pilot" flights I spent a few hours doing steep turns, stalls etc. followed by circuits with tailwinds, crosswinds, gusty winds. Doing circuits tighter and tighter to the point were the whole circuits was one low(ish) level turn etc.
I did this stuff making sure that I was doing enough to force concentration without doing so much as to cause fear or panic and I believe it really made me more confident and better for it because I felt far more comfortable doing anything else afterwards knowing what the limits of myself and the aircraft truly were and what I was comfortable with doing. I highly recommend doing the same.