Hence why you should always think about how much the item is worth to you and how much you are willing to pay. Put in your max bid and then forget about it. If you win then you paid the price you are willing to pay. If you lose then you know you didn't go over the price you were willing to spend
The thing is, people are often willing to pay £10 more than what they are really willing to spend just to get it there and then. So if you are bidding early, you give other people an incentive to go "ooo I could win it if only I pay just a little bit more...."