O'Donovan told BBC Radio Northampton: "I said after Rotherham in February that it was going to take a bit of getting match fitness.
"I just want to play more games. I want the season to go on and on."
O'Donovan has scored six goals in 17 appearances for Northampton
since his January move.
It is his best goalscoring spell since nine goals in 15 appearances for Hartlepool in 2010.
"I'm on a good spell of form now," said O'Donovan.
"I'm starting to feel good now, feeling fit and sharp, and getting the odd chance."
The Cobblers will take a slender 1-0 lead into the second leg of the play-offs against last season's finalists Cheltenham.
Adebayo Akinfenwa was kept out by an excellent save from Scott Brown but O'Donovan is backing his strike partner to end a 13-match goalless run.
"We've got quite an experienced side and the manager's been here before so hopefully we can get over the line," he said.
"Bayo was so strong. I haven't see him be that strong in quite a while with his back problems. I could feel a goal coming for him all night but you can see him coming back into form which bodes well for us."
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