The Royals, now assured of a play-off place, need to beat Birmingham City at the Madejski Stadium - and hope Sheffield United fail to win - to pip second-placed Blues to the second automatic promotion spot.
And Coppell added: "I was manic depressive in February after we hadn't won in a month but no more than usual.
"We want to finish as high up the league as we can. We have a dog's chance of success but that's better than no chance."
Coppell has previously managed Crystal Palace, Manchester City, Brentford and Brighton.
He has been in charge of Reading since October 2003 and guided them to the Premier League in 2006.
They were relegated at the end of last season and Coppell was ready to leave the club but changed his mind, claiming the goodwill of Reading's supporters were a pivotal factor in his decision to stay.
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