What’s the best advice you’ve ever gotten? What advice would you want to impart on young scientists who are coming up?

My undergraduate advisor would tell me to 'Just do it' whenever we were confronted by some difficult or tedious task. People get the idea sometimes that science is all about discovery and requires being super smart. Mostly, however, science is persistence and determination. That is the sentiment behind Thomas Edison's quote, "Genius is 99% perspiration and 1% inspiration." Of course, that 1% of discovery is one of the rewards of science.
My advice to young scientists is: be curious. Ask questions about how and why things work. Not only will you learn something new, but you might find out something other people have missed. Discovery is one of the exciting parts of science.