Well ive only been playing for 4months, so ive only played infront of like 5 mates at the most, but i think its the same. I used to get nervous and sweat like hell!! But just remember, any mistakes are just artistic licence and your mates prolly cant play guitar!!
But the main way i personally dont get nervous is because i feel proud to be playing a slash solo and doing it justice. ( i play mainly guns n roses stuff) I think about ex girlfriends and why i learnt the guitar tunes in the first place, for sweet child o mine especially, the intro is me n this girl vicky meeting, the bridge parts are the good times, the solo (non wah part) is our argument, and the wah bit is the break up!!

Later Axl