Sharp told the Professional Footballers Association's official website: "My appetite is back for football. I've got a smile and the fans have been great to me.
"I was going into training every day knowing I was getting nothing out of it. I was on the bench and not getting on, or just not involved again."
The Sheffield-born, lifelong Blades fan added: "I'm not going anywhere until the end of the season. I'll enjoy it and sort things out after that."