As a developer...

1. you have to understand people that dont know how to explain their necessities.
2. you have to imagine what clients really need.
3. you have to deal with people who think they know how to do something because they read it in a blog / saw it at a conference / a friend told them.
4. you should try not to hurt (their) feelings.
5. you have to be flexible.
6. you have to integrate code / modules / libraries that are not written by you, but you have tu trust them as if they were.
7. you constantly need to learn the ultimate technologies.
8. you have to deal with problems arising during development within the same deadline (or release crap).
9. you should quit finger-pointing!
10. you have to focus on really important things (for whom? the client, your boss, the team, the contractor).
11. you have to be willing to share your knowledge and teach people.
12. you have to surround yourself with people who know more than you.
13. you have to be humble but not stupid.
14. you have to be intelligent in discussions (they are good).
15. you have to predict how the product will evolve and reflect that in your code (have told you we are magicians?).
16. you have to predict how much time you need to learn a specific technology.
17. you have to accept bugs, and deal with them.
18. you have to accept your mistakes, and deal with them.
19. you have to understand that programming languages are not girlfriends, so don't marry one.
20. you are part of a team, so ask for advice & help.
21. you have to be humble (yes, twice).
22. DRY.
23. you should realize you are a nerd; deal with that too.
24. you should be proactive, not reactive.
25. you have to measure everything (backend, middleware, frontend, network), even though you didn't do it.
26. you should know that there are times to be creative and times to be effective - creative efficiency is not the same that Efficient creativity.
27. you have to keep yourself motivated.
28. you have to estimate stuff that you dont know how to do.
29. you have to keep your eyes in the goal.

30. you have to kick ass.

http://as-a-developer.net

thanks to @yo_gero