The Nigeria international had been given a belated holiday after playing in the Confederations Cup but was recalled at short notice last week for the first leg of the Hoops' Champions League second qualifier against Cliftonville in Belfast after manager Neil Lennon found himself short in defence.
A 3-0 win over the Irish part-timers makes tonight's second leg at Celtic Park a formality but Ambrose claims he is able and ready to face anything between now and next May.
"I feel great," he said. " I had four-day break. That is normal for me.
"When I was in Nigeria I was working hard, preparing myself so when I came back I could start playing because I knew there was no time for pre-season.
"I am a professional player, I keep my body fit for the rest of the season."
The Parkhead side reached the last 16 of the Champions League last season before exiting to Italian giants Juventus.
On the domestic front, Lennon's side retained their Scottish Premier League title and won the Scottish Cup and Ambrose is confident the Hoops can improve on that this campaign
Midfielder Victor Wanyama has left for Southampton and it is expected that top scorer Gary Hooper will leave the club although he is back in the squad for the game after recovering from a groin injury.
"We set the target last year and we want to do better this year," he said.
"I don't think we have (the squad to do that), I believe we have.
"I believe in what the manager has seen in them (new signings) and I believe they are good players, that is why they are here.
"We never rely on just two players, we rely on the whole team and the people on the bench.
"We can see the qualities of the players and we can do even more than what we did last year, if we put our mind to it and be determined to work harder."
Reds manager Tommy Breslin is hoping his side do not end up as cannon fodder for the Scottish champions tonight.
"We are not going out to roll over," he said.
"I don't want to be on the wrong end of a drubbing and that could be a possibility.
"We are here to try to frustrate Celtic and try to give a good account of ourselves.
"Let's put it into perspective, we are a part-time club. I feel we have the best players for our league but we are coming up against a team who were in the last 16 of the Champions League not so long ago. That's what we are up against."
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- Neil Lennon