Gannon was named as successor to Mark Cooper who was fired from the managers job on Monday.
"I want an enjoyable end to the season and hopefully some success on the way," he told BBC Radio Cambridgeshire.
"I'm an optimist, but I'm also a realist and I don't expect us to get 12 or 13 wins and I don't want false optimism.
"I'm here to make a difference and bring back some respect, credibility and pride back to the club.
"I'm responsible for the next 18 games and will be working hard to make sure we get something out of these matches," he added.
"I think the players want to prove themselves at this level and certainly I want to prove myself at this level."