I was out cycling with my mates and one (much more experienced than me) challenged me to follow him down Butser Hill. Being naive, I accepted and got a bit out of my depth, and I was wondering if you could tell me where I went wrong. So could you please watch the video and give me some tips or alternatively just laugh at me

Here is the footage:
Crash Down Butser Hill - YouTube

Many Thanks in advance WillBryan.