The center turned down a lucrative contract with the Los Angeles Lakers to make the move, having recorded his lowest points per game average since the 2005-06 season while with LA.
The 27-year-old told The AP: "I'm in a better place mentally, physically and spiritually now. The situation in LA what happened is over with.
"It didn't work out on both sides. So we have to move on. It happens in everyday life. People decide to do different things with their lives. It's just that when you're NBA and at the top of your game everybody wants to know what you're doing."
Howard leads the Rockets in blocks per game during the pre-season.