At the office: realize that if you don't have confidence, you are unlikely to get actively anywhere further (promotion, enhanced responsibilities). In a word,

At the office: realize that if you don't have confidence, you are unlikely to get actively anywhere further (promotion, enhanced responsibilities). In a word, cross the door, then people will hold it open for you. The opposite doesn't work. For everything else: as said by others, plan, iterate, think, correct, repeat.