Central defender Johnson made the ?5million move from Birmingham to Molineux during the summer and was instantly made captain by manager Mick McCarthy in place of Karl Henry.
But he struggled to reproduce the form shown with Blues and was dropped for the 2-1 home win over Sunderland at the beginning of December and replaced by veteran Jody Craddock. And Johnson said: "Being left out of the team was the worst moment of my career to date."
He added: "Being left out through not playing well enough had never happened to me before.
"It hit home big time. I certainly don't want that feeling again. I'll be doing whatever it takes to make sure it doesn't happen again."
A hamstring injury to Craddock meant Johnson returned to lead the side in the next game against Manchester United.
The former Cardiff player showed signs of being back to his best during Tuesday's shock 1-1 draw with Arsenal at the Emirates Stadium.
Johnson said: "I was happy with my performance. My performance levels have been mentioned before but I was a lot happier with my game.
"That is more like me. Hopefully I can keep that up going into the new year.
"It's about getting my performance levels to be good and consistent and hopefully, going into the new year, I can keep it like that."
Source: PA
Source: PA