First impressions count.

Firsts and lasts tend to stick in the memory hence the advice to make a good first impression. Job interviews, dates, first day at a new place is the time to be prepared and put your best foot forward. It is also the time when you are most likely to be nervous but with a "little forethought you can save much afterthought". But if it does go wrong don't be too worried, "to err is human, to forgive divine".