I'm a fairly late-comer to the game so I'm only sitting on 8 wins from 56 races; but if you want to win more often (assuming you're competent to begin with) I'd recommend NOT qualifying at 100% of your pace, super maxed out, full commitment - because you will not be able to consistently lap at that time.
I often race just to race, so I don't tend to bother with qualifying. I might do 1 lap, but I make sure I set a time that I can consistently hit +/-0.1 pretty much every lap.
Most other drivers in your race won't be able to consistently get within 1 second of their quali time, so assuming you're able to drive consistently you'll have a lot more pace than those around you.
I can start 10-15th and still have a good chance of taking the win so long as the race is >3 laps and I don't get taken out early, plus you have a great race through the pack anyway!
As others have said, stick to the same race/car combination for your session, and your quali time will naturally improve anyway, but this method ensures it improves in sync with your overall pace, not a freak one-off that you can't replicate.
Main thing is to just enjoy the race, and accept you won't win every event you enter