Pulis knows his Potters have not been pulling their weight recently but believes there are reasons behind their recent slump.
He said: "There are going to be years when you're not having the best of times for whatever reasons.
"You might have injuries, you might have players who lose form. Within the group there may be things going on in players' lives. Players lose confidence, don't play as many games as they want, they're down in the dumps and lose confidence.
"There are always certain things which affect players' performances. It's a difficult balancing act which we've done pretty well for seven years. There are times when you think you have it cracked, then it drifts and ebbs away.
"Clubs have different levels they aspire to which are determined by the amount of money you have and the size of your football club.
"You can progress some clubs so far, then you hit a ceiling. Once you hit that ceiling it's difficult to start over again and hit that ceiling again and again and again.
"You have to be at your best every time, in every single game, every single year to hit that ceiling and this season we have not always made that mark."