It always helps to ease the nerves when you guzzle down a few cold beers before you go into anything like that...
I don't think this is good advice regardless of age. If someone is serious about being accepted in a professional capacity - being under the influence or even having booze (or weed) on ones breath is not a good idea.
Maybe in a band situation -at rehearsal or on stage (if the band leader/club owner allows it) - but in a production capacity, no way!
I use to do a fair amount of jingle work and small post production gigs - if a client/music supervisor even suspected that I was not 100% in control I would have been booted in a second - and I think it's safe to say the engineer would not have allowed me within 10' of the control board.
If you have chops - you don't need liquid courage!