Allmendinger says he has unfinished business in NASCAR

The American was dropped by Penske after testing positive for a banned substance in July.

He was reinstated two months later after taking part in NASCAR's 'Road to Recovery' programme, and made four starts for Phoenix Racing.

Allmendinger is without a full-time drive for 2013 at the moment, but this weekend he will attempt to win the Daytona 24 Hours for the second year running with Michael Shank Racing.

"I have a lot of unfinished business [in NASCAR]," he said. "That's not the way I want to go out.

"All the hell in my life started in the July Cup race [at Daytona]. I reflect on it every day."

The 31-year-old, who was quickest on the opening day of testing for the 24-hour race last weekend, added that he was struggling to adapt to starting the year without a championship to focus on.

"I'm not going to lie and say I wake up every day joyous and happy," he said.

"Some days I have to find self-worth in what's going on since I've been so used to - especially at this point - being at a race shop getting ready to go testing and jumping in a [Cup] car."

Allmendinger says he has stayed in contact with the Phoenix team, and he believes that he did learn from the difficult time he went through in the second half of the year.

"I'm a lot better person now than I was when I had just won this [24-hour] race last year," he added.

"I've learned from everything. All the things I've been through, I've got better from.

"The good thing is I'm here [at Daytona], the race car's fast and we have a chance to win this thing."