I have kicked myself for buying the wrong knife, for spending too much on knives, for spending too little on knives, for passing up a good addition to my collection, for not taking enough advantage of a good deal, etc., etc. Basically I kick myself virtually everytime I have a knife related thought. And on those rare occasions when I decide a sharp kick in the butt is not warranted the wife is more than happy to make up the difference.
Fortunately, I have grown immune. I may not be perfect by I am sure having fun.