The Harlequins ace was handed a six-week ban at the turn of the year after being sent-off during his club's 30-29 loss to Sale Sharks in the Aviva Premiership for a dangerous clear-out of a ruck.
The 27-year-old was subsequently forced to miss England's opening two matches of this year's Six Nations against Italy and Wales, although his absence did not affect the result of those matches, as the reigning champions emerged victorious in both games.
Marler is now available to return to the England fold for their clash with Scotland at Murrayfield on February 24 and he admits it was hard to watch the Wales game in particular from the sidelines.
"England v Wales is my favourite fixture, the game I love playing in and being involved in most. I was gutted not being a part of it," Marler said.
The prop confirmed he must improve his disciplinary issues going forward to avoid similar suspensions, particularly as he could not argue with the original decision to ban him for six weeks.
He added: "It sticks with me that I really need to knuckle down now because I am missing out on these things that I really want to be a part of.
"It was fair - I've been cited twice in the last six months and spent nine weeks on the sidelines. There was no real argument from me."