Lots of good information on this thread.
2 things which I found really helped me a) get better/faster/confident b) enjoy it more
1: Look where you WANT to go
Sounds stupid, but its really not. It was a road ride that taught me this lesson most. I used to find that when going round a corner fast, I couldn't help but drift out to the edge of the road and rough stuff. It even had me off the bike once at speed. Through talking to others I was told to
- bend the inside elbow and drop my shoulder into the corner
- turn my head and shoulders to where I want the bike to be going, and not to look where I think I may end up ( like the verge ).
After doing that, I found I could corner faster and tighter, and since then I've not been drifting out as much. People have already said this on the thread, the wheels do slip a little from time to time, but if you looking where you want to go, for the most part the bike will simply follow.
2: Slow speed technical climbing
Granny gear stuff over bumpy bumpy things. I used to be absolutely rubbish at it. But by getting out there and practising on the bike, I have become a lot better at it. I now am placing the front wheel where I want it to go, and knowing what to expect when the rear wheel hits bumps etc etc. I find my body moves all over the place and my arms are working hard and it didn't come straight away, but over time my balance has greatly improved and the ability to get up awkward little bits has increased. It means I can make steep climbs without dabbing and stopping and getting frustrated.
Both of these things make rides that bit more enjoyable.
I dont worry about being the fastest. I weight 15.5st and have a heavy full susser. I find finishing the ride having enjoyed it the main thing, not completing it 30seconds faster than the day before.