When I was serious riding, I rarely ever got this 'manic drivers/ Incosiderate drivers etc etc...I generally found most drivers ok.
I used to rush hour commute in Peterborough for years, long countryside rides for hours, totalling 6k miles a year, I maybe had one stupid thing happen once a year. A good few disrespectful passes of course but not dangerous ones. I dont know if it used to be my road positioning, confidence, awareness, speed, I just dont know but generally I loved my cycling and rarely had occasions where I thought FFS, is this all worth it ?
I agree with showing respectful drivers your respect and thanks with a thumbs up or wave, done it many times...including stuff like hopping up on a path and waving lorries by if the road is narrow, then pop down behind them...I might have right of way but theres no point holding 32 tonnes of lorry up for 1/4 mile while I steadfastly claim what's mine...its about sharing the road and spreading the word we're not all zealots.