I passed my club's solo certification after about eight to ten flights. I remember the first true 'solo' flight I took after getting signed off by the instructors I was so nervous that I took off, flew one circuit and then landed again just so that I could get it out of the way
Now I've had ten flights truly solo and I'm really starting to enjoy the flying, but I still make sure to listen to that little internal voice that says 'nah, I don't think you should do that.' I figure the minute you stop listening to that little voice is the minute that you convert your pride and joy into matchsticks
Cheers,
Neil.