The 22-year-old missed all of Celtic's games in September after an early-season back problem was compounded by a virus that saw him spend time in hospital.
The winger returned off the bench against Barcelona and Motherwell earlier this month and is keen to start his first Scottish Premiership game since the season opener against Ross County, when Celtic face Hibernian at Easter Road on Sunday.
Forrest, who was left out of the Scotland squad to face Croatia to help him regain his fitness, told the Celtic View: "It's just been bad luck getting not well and having a wee niggle here and there and I just need a wee bit of luck now to get a run of games.
"We have a lot of big games left and once all the boys are back on Thursday and Friday we can look forward to the next few weeks.
"When you haven't been well, you don't want to come back and do too much, so it's been a good wee break and (I) have been able to do some hard work.
"I feel better in training and I just need to try and get back up to speed fitness-wise."