Guthrie looked to be heading for an early exit from the Madejski Stadium following a string of bust-ups with manager Brian McDermott.
He revealed: "I did think my Reading career was over. I had to start from the bottom and earn everyone's trust.
"The only way I could do that was to play, work my socks off for this team and add my little bit of quality.
"I'm getting back to my best and I will get stronger. It feels nice after what has gone on and I think that is reflected in the way the team is picking up too."