Well I am definately a pub player
There is absolutely no doubt that confidence and belief are 2 major factors in throwing good darts.
I regularly play against me brother and he is far better than me, but if I nick a leg or 2 off him then I find my darts improve, no doubt due to my increased confidence and the belief that I can throw well.
Unfortunately I can only keep up my A game for maybe 30mins or so, either due to me brother regaining his confidence or me losing concentration.
This works the same in a league match, however I can bring on the confidence with a couple of beers but while my confidence rises my concentration becomes less focused - for those few legs where the confidence and focus is in tune with my concentration I throw brilliant (for my own standard) and I think this is the reason, even when I am throwing badly, that I keep playing, knowing that at any given time, the focus and the concentration will align making me one very happy darter, even if it only lasts half an hour