The 23-year-old made his debut for the Blues in their League Cup third-round victory over Wolverhampton Wanderers on Tuesday after fully recovering from a hamstring injury.
"It was a hard time doing the whole pre-season and then the US tour, then the injury, but it's football and it happens, now I'm happy to be back," said Marin.
"Of course it's not nice, for any player, there is never a good situation to be injured but now I feel good and can forget that time, it's in the past and I look to the future.
"I have no targets, of course I want to play as much as possible and now I am nearly 100% fit again, it makes me happy and I want to play. The injury is done."
Marin joined Chelsea from German club Werder Bremen in the summer.