Ian
Never set daily targets, use weekly or monthly ones instead.
The reasons are if you set a daily target and you don't reach it or when you are knocking you know that you will not reach it, you attitude can change and people pick up on these signals, the same applies when you are picking up customers right, left and centre, you start to feel invinceable and then you start to get more, because of the positive signals that are flying out of you.
If you have a target of wanting x amount of customers break in down into a easly managed targets that are achievable over a certain period of time.