You get involved with someone you don't care about just to be with someone. Your signifcant other has a habit that annoys you more and more each day. You have annoying habits too. You tell the person what annoys you and why. Your boss has assigned you your first big project, and the success or failure of the project could make or break your career.
Nervous energy helps fuel the process.
You push it aside, you'll get to it later. You spend the next week planning the project out in careful detail before telling anybody. You take a few minutes to relax, give yourself time to think, bounce ideas off a colleague, and decide to pursue the idea that makes you feel most confident. You regain your poise, laugh at yourself, and continue on your way. You look around and give anyone who is looking at you a dirty look.