Number two: pressing on to planned destination when the weather is getting worse.....Never be ashamed to return to base, don't worry what anyone else will think of that sensible decision.
The one that nearly got me. As it got worse, I clearly remember the image of the clear airfield I had passed and saying, no I wont land, it will get better. It did not, and very nearly killed myself that day, and I learned a lot about, not only weather, but myself. Went straight out and got an IMcr.