Things I wish I could tell my 18 year old self.

1) Accept you will make mistakes.
2) Truly learn the language you are using.
3) Write idiomatic code for the language you are using.
4) Be upfront about not knowing something.
5) Don't let not knowing something stop you from learning it.
6) None of us knew X until we learned it.
7) Understand your strengths and weaknesses as a developer, play to them.
8) Be willing to try new things.
9) X language isn't ALWAYS the best choice, X paradigm isn't ALWAYS the best choice. Choose wisely.
10) You won't know everything, but you might know more than others.
11) Your ideas and ego don't matter more than ensuring the product works.
12) "Perfection is the enemy of the good [enough]" - Voltaire
13) "Perfection is not achieved when there's nothing more to add, but when there's nothing more to remove." - Einstein.
14) Conflicts happen, deal with it.
15) Develop a toolset and really learn them.
16) Try new tools, they may prove better than what you were using.
17) Don't manage your own memory unless you absolutely have to, you are probably not smarter than the collective intelligence of the team that built the various garbage collection methods.
18) People can be dicks, especially online.
19) If you are new and people are being dicks to you, did you skip past the irc message about etiquette? If you did, you're the dick in this situation.
20) It can be tough, but it is fun, so have fun!