Kelly made a successful playing comeback last week in the friendly win at Shamrock Rovers.
"The last few months have been difficult," admitted the 24-year-old to liverpoolfc.com. "It was about being able to understand that you can't play in games when we're playing one game a week.
"But it's definitely strengthened my character. I've just kept my head down and I've been trying to do extra work after training and in the gym.
"The chance has not arrived this season, but I know I have three years left on my contract and that the chance will come. The manager was trying to win the league and he couldn't introduce me when I wasn't match fit. So it was difficult.
"As a football player from the age of seven, training through the week and having the game at the end of the week, that's all you want to do - play football. So it was frustrating, but I've come through that now and I'm looking forward to playing games next season.
"I think everyone's ready for a break, but I'm ready to hit the ground running. I'll have a week or two off and then get back at it."
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