Berahino pushed for a move to Tottenham before the transfer window shut in September and threatened to go on strike, though he eventually backed down.
The Burundi-born forward's future is up in the air once again ahead of the January transfer window, with Chelsea the latest club linked with the striker.
Pulis, however, is confident the 22-year-old can deal with any transfer speculation this time around.
"He's had two or three windows now - that he's experienced this situation and he'll be a lot stronger and a lot more understanding of what goes on in terms of what's spoken about," Pulis said as his West Brom side prepare to host Arsenal on Saturday.
"I pulled him to one side and he made me a cup of green tea.
"He had 20 minutes in my office, he understands, he knows the score. But it's taken a while to get him back to thinking straight."
Berahino has struggled for form and consistency since his move to Tottenham fell through.
He has scored just three Premier League goals this season, having netted 20 in all competitions last term.
Pulis added: "He's still not near what he was at the back end of last season.
"His form has dropped and dipped but the penny's dropped and he has to be switched on.
"The kid realises and understands that - irrespective of what we do as a club - he's got to be right in himself.
"He's definitely got his head down but it did affect Saido.
"That was a deep cut. It was something he hasn't experienced.
"The opportunity of going to a top four or five club, and not getting a move that he thought was going to just happen, really shook him.
"The club didn't think it was right and the club had the responsibility and the right to make the decision they made."