Does anyone have started mistakes they made that others could learn from? I know I made the mistake once of thinking I did not need a saddle, and hours later after riding, I was sadly mistaken and full of pain.

I remember one time I went out once on a ride. It was a nice day and I left mid afternoon. Well I forgot my jacket and was literally riding into the night. I got home after dark and had the time of my life. The only problem is I was freezing because the sun had gone down and it got cold quick.