The young full-back made 14 appearances, scoring once, as the Lions dragged themselves away from the drop zone thanks to an eight-match unbeaten run stretching back to March.
On the season's thrilling final day on Saturday, Ryan was a late substitute as Millwall beat Bournemouth to guarantee safety as an injury-time equaliser from Birmingham at Bolton opened the trap door for Doncaster, who lost at champions Leicester.
Now back in the fold and training with the first team here at Spurs, Ryan was left to reflect on a 'positive season'.
"It was a a great experience," said Ryan, who caught the eye with a substitute appearance in our Europa League win against Anji back in December.
"There was such relief at the final whistle and it meant so much to everyone. Everyone at the club told me that they never do things the easy way at Millwall!
"In the end the team finished well but even when we were at the bottom of the table, it was always about winning the next game, not looking down at relegation. Once we got a head of steam up, we never looked back."
Ryan enjoyed the second loan spell of his career, stepping up from a shorter period League One at Brentford in 2011-12.
"It's a different style of football, a lot of pressure on every match and more physical," he added. "It's much tougher on the legs - you come in after a game and think you're not going to be able to walk for a couple of days!
"I felt I did okay though and thoroughly enjoyed it.
"I knew what to expect because a few of the lads have been down there like Harry, Andros and Jon Obika. The lads were fantastic, all accepted me and the fans were great. I gave everything and they take to you if they see that effort. I feel I’ve improved my all-round game with the experience and that’s the main thing."