Pulis, who helped West Brom finish 10th last season, said the fans have short memories and expectations at the club have gone through the roof.
"What happens is when you're at a football club, and I've been here nearly three years now, you take the club up and take it up and take it onwards and onwards," he said.
"We finished in the top ten last year, we've brought some good players in and everybody was talking about us finishing in the top eight. That's the expectation.
"That's soon forgotten if you go on a bad run. And supporters are unforgiving, that's not just at this football club, it's at every football club."
Pulis called West Brom's two wins from last 20 league games "one of my worst ever runs as manager".
Although he has improved the club's status from a relegation-threatened club to a stable mid-table outfit since his arrival in January 2015, the manager was aware that his future would only be decided by the results on the pitch.
"Supporters go off games. There's never a thought of what happened before, it's all about today. It's not about yesterday," he added.
"Irrespective of what I've done previously, they look at the results you've had over a short period of time. I've been in the game a long time, it’s all about results."
(Reporting by Hardik Vyas in Bengaluru; editing by Amlan Chakraborty)
