Like other collectors, I focus on completing a set or sets of coins and occasionally will fall under the influence of an impulse buy that has nothing to do with any of my current collections.
This is not an uncommon practice as one can get tired from searching for that "right" coin to add or complete a set and buying something different is a temporary but wonderful distraction. It was one these "wonderful distractions" where I discovered I discriminate against certain coins.
When my eye tended to wander it was always towards large world (crown size) silver dollars or U.S. key/semi-key coins and I would quickly skip past or scroll by anything in between. Not sure how long I have been this doing but I caught myself recently on e-bay by pure accident during one of my lightning speed screen scrolls I accidentally clicked a listing. What popped up was a beautiful 1800's Portugal 500 REIS silver coin, which I ended up buying for $14.
It was not a huge piece of silver and it was not even close to the definition of rare. Wondering what else I have overlooked because it was not big & flashy really hit me between the eyes. Once you start looking at a wider field the number of interesting designs expands by 10 fold. Going forward I will not take any coin denomination, size or even composition for granted during an impulse buy.
Of course this could lead to the new issue of becoming too distracted to complete the set you had originally started out on but with so many coins out their to appreciate we'd be silly to not make the occasional impulse buy. Maybe a better way to look at is getting ideas for a new future set :)