Henin, 27, told a news conference on Tuesday she "grew up" during her absence from the court and can eclipse the standard she set in winning seven grand slam titles.
The Belgian will play in next week's Brisbane International and the subsequent Sydney International before contesting the Jan. 18-31 Australian Open as a wild card.
While keeping expectations in check, she said a second Australian Open title was "possible."
"I believe I can be a better player, I believe I can use my experience more than in the past," Henin said. "When you are into (playing tennis at) 200 percent you have no time to realize it. You are too involved all the time and all this time off helped me to realize everything I achieved.
Henin said her absence from tennis has given her personal insight and perspective, adding that she didn't watch a set of tennis in the first 12 months after retirement and now returns to the sport refreshed and self-aware.
"What I can say is I know myself much better and that's the most important thing," she said.
Henin appeared more relaxed at Tuesday's news conference than in the past, when she was often perceived as aloof.
"I'm 27 now I just want to live my second career differently to how I did in the past," she said. "It's been a great experience to go out of the tennis world for 18 months and to come back because I feel I grew up."
Henin, who won the 2004 Australian Open, will use the Brisbane International to find her tournament rhythm. She showed early form, and a stronger serve, when she beat Russia's Nadia Petrova in an exhibition in Cairo earlier this month.
"Of course I will need some time to be 100 percent, to be the level I was when I stopped my career, but I'm ready to live anything here," she said.