The Scotland international said: "I was getting a bit frustrated kicking my heels up the road (at Sunderland), but that's the way football works out at times.
"When I was told about the chance to play for Plymouth, my first thought was that it would be good to get back playing games. I have been given the opportunity to come down here and hopefully, I can make the most of it.
"On one hand, it was difficult going straight into the team at very short notice, but the team have been doing well and I think that makes it easier.
"If I had been coming into a struggling team and the players' confidence was down then it would have made it a lot harder. But, by all accounts, the team have been doing well so it was easier to fit in."