A source tells ET that Carter is focused on his health and new music, and is set to release his first album in 15 years.
Aaron Carter can't wait for 2018.
After several months in treatment, the 29-year-old singer has left his health and wellness facility -- and is looking forward to the future.
"If there's one lesson I've learned this year, it's to not dwell on the past, but live for the future," Carter tweeted on Thursday. "I'm so excited for what 2018 will bring for my musical career and for my life."
ET has learned that Carter gained 40 pounds since entering the health and wellness facility in September, with a source sharing that Carter is now fit and has been eating healthy. According to the source, Carter will also be releasing his new album in 2018, which will be his first new album in 15 years.
Carter has kept his fans updated through every step of his treatment, tweeting on Sept. 22, before entering the facility, that "Only I can change my life. No one can do it for me."
The "I Want Candy" singer briefly left the facility on Oct. 6 to deal with "several legal and personal matters," his rep told ET at the time, sharing that he returned to the facility a week later, on Oct. 14.
Weeks later, he was "back in the lab" and working on new music.
"Today was a dream come true! Can't wait to do it all over again tomorrow. goodnight," he tweeted after a day in the studio.
See more on Carter in the video below.