If you had to do something for the greater good, even though the thought, let alone the deed traumatised you... would you?

I know a lot depends on what it was and how important it was.. but say something you really hate, like needles/injections etc. would you do whatever it takes? And have you ever surprised yourself by doing something that makes you feel totally nauseous, that you never thought you could?

I had to do something I find totally sickening today... I am not proud of myself for doing it.. just glad it's over :P