Certainly don't beat yourself up! The fact that you have identified these "mistakes" means that you're less likely to make them again!
Last time I flew (after a 3 week break), I made my worst error since gaining my PPL. During my cockpit checks instead of setting the altimeter to the airfield elevation, I managed to add 1000ft to it! After takeoff I glanced at the altimeter for a cue to raise the flaps and I got a shock. Something wasn't right! I couldn't have reached that height already, was the instrument faulty, oh dear! When I looked at the sub-scale and saw 1028 I realised that I had made a mistake. No A/G operator on duty at my airfield, so I leveled off to avoid busting the airspace above and tuned the ATIS of the nearest airport for the QNH. Had me sweating and I felt like such a pratt!!! Suffice to say I won't be making that mistake again in a hurry.
