One word I take pride in not calling myself is an 'expert'. You might think 'What the hell are you training people for then?' I'm not saying that I don't know my job, that I don't know the principles of strength and conditioning, about energy systems, about assessments and writing appropriate programmes for athletes........I do........but I will never label myself an expert.
The leading people of any profession, and I mean the very top people, adopt a 'white belt mentality' attitude. They are constantly looking to improve, broaden their knowledge, prepare to make mistakes. Their mind is open and with that is a need to be always learning. Scientists believed the atom was the smallest thing known to man but an open mind and an thirst for knowledge led them to discover that when they split it, a whole load of other crap was found inside, changing everything they knew up to that point. To me, someone who says they are an expert has closed their mind to learning and challenging their beliefs.
Adapt this to your everyday life: in work and recreational time. You will live so much more.
If someone down at the gym offers you advice, listen to what they say. You've been training for 10-20 years and this guy looks like he's just left school.......so what? Don't be arrogant enough to think you know everything someone younger than you has to offer, don't be that guy.
"The more I read, the more I acquire, the more certain I am that I know nothing". (Voltair)
Do a little research, find some theory to it, read and understand, interract with others who disagree with you and do it always.....that's where you learn.