I used to get annoyed when that happened to me but it was usually something I really wanted and if I'd hung on Sale Watching the item may not have been left in my chosen size or colour so I stopped fretting about it. This can spoil the enjoyment
I usually do better when I like something but not enough to click Buy Now And Put It In My Basket At Once and weeks later I see it reduced in price, hover a bit, think do I really like it that much and make the decision!