The finger-spinner made the comments after putting in his best bowling performance in Australia with 3-101 off 26 overs during the third day of the first Test here Friday.
Harbhajan's performance on Friday made him only the fourth Indian bowler to pass 250 Test wickets.
He now has 251 wickets and lies fourth all-time in Indian cricket behind team-mate Anil Kumble (591), Kapil Dev (434) and Bishen Bedi (266).
India have to defy Test history and score 493 more runs to beat Australia over the two remaining days of the Boxing Day Test.
Harbhajan's Test career high point was his 32 wickets at 17.03 in the three-match home series against Australia in 2001, a remarkable feat he says he has struggled to repeat during his career.
"From the time I took those 32 wickets, whenever I didn't get wickets, people expected me to do the same thing, it's not easy to do things like that.
It happens once or twice in a lifetime," the 27-year-old said.
"It's good to have expectations but you can't really do anything about it, you just go and try to bowl well for my team.
"I've played enough cricket now and I know in the tough conditions how to handle things. I was very raw when I came in to play in 2001, I was young and all over the place.
"There wasn't that much responsibility for me then and things have now changed and there is a lot of responsibility not just in bowling and batting, but also off the field."
Harbhajan captured the big wickets of Matthew Hayden (47), Ricky Ponting (3) and Adam Gilchrist (35) to make Friday a special day.
Harbhajan claimed his 250th wicket with the dismissal of world cricket's No.1 rated batsman Ponting for the sixth time.
"There's no doubt that Ricky Ponting is a very good player, but I have some sort of success against him, I don't know how and why," he said.
"It's always good to get good batsmen out and I'm very happy to get his wicket again and it was my 250th Test wicket and that means a lot in getting a great player out."
Harbhajan won't discount India's hopes of overturning cricket history and winning the first MCG Test.
"Obviously, it's a stiff target, but I won't say it's not achievable," he said. "With the kind of batting lineup we have, if we play to our potential anything can happen in cricket and this is a good wicket to bat on.
"I'm sure our batsmen are looking forward to going out and showing some character tomorrow.
"We're here to win the series, we're not looking to draw this match and we'll try our best to win this game. We're going to give it our best shot."