Hey mate, from what I see the first thing is sloppiness-Holding accurate heights, staying in balance, LOOKOUT, etc. Then many fail to practice emergency procedures. Precautionaries, EFATO,EFIC,PFL's etc. Once in 2 years they'll get a reminder with a BFR. But Murphy doesn't care about that...!
The other areas are adherence to correct radio phraseology and keeping brevity in same, and awareness of subtle changes that have occurred in regs and ops ; for example,in flight above 5000' requirements and general CTA avoidance and what we can ask for/can't ask for and what boundary tolerances we need to observe.
The line between a "safe" Pilot certificate standard, and being the best we can be is often a blurred and individually interpreted line, and IMHO if you're not trying to improve in every flight then inevitably you are going backwards, if through nothing else than simple complacency.
Be passionate about your flying, and even if it's just for fun be professional in your delivery. the lapels that matter are the ones you wear in your behavoirs -not on your shoulders.
Food for thought.......?