A wise man once said - Ends 6th May

[Drake.]

Best: "Believe in yourself"
Worst: "Google your symptoms"

Bonus one that I like: "If you don't try to build your dream, somebody else will pay you to build theirs."

[!x!dude!x!2]

Worst : "Just give up"
Best: "All you gotta do is believe in yourself"

[Bankai90]

Best
- Time is gold.

Worst
- Sleep, eat, rave repeat during your free time.

[Liva]

For me personally it would have to be 'Don't do what your friends are doing'. I've followed it, found that I don't feel comfortable around people and try to avoid doing that thing again.