My first day at a big4 consulting firm I was given the best advice I've ever received. "You need to get comfortable saying no to requests that aren't important"

My first day at a big4 consulting firm I was given the best advice I've ever received. "You need to get comfortable saying no to requests that aren't important". It's so easy to drown in consulting by trying to please everyone. Sometimes you just need to say "no, I can't do that now I'm too busy.".