Wow, what a write-up! Just about every racer you care to ask, who has done a season's or so of racing, will have very similar experiences. I know this isn't much of a consolation now, but everyone experiences the "highs and lows or racing" at one point or another. The highs are fantastic, the lows are very demoralising. You will have another high, though, and probably very soon. It's the nature of racing.
3 weeks ago at Cadwell, I had weekend like yours, save the trailer incidents, crashing in the warm-up, and finishing only 1 of 8 races (7 DNS). Contemplated chucking it all in for about a day or so. A week ago at our Donington round, our team swept the podium in the newcomers class. Much better than any happy pill.

Much more addictive and expensive, though.
Best of luck at Snetterton.
P.S. What dust caps are you on about?
[Edited on 8-6-2005 by Felix]