He has come through some dark times, but now plays for England Deaf Rugby Union as well as working for Sale Sharks Forces, a programme for veterans just like himself.
Sports recovery can take many forms, and for the dedicated few, that means reaching an elite level.
So when Mr Monaghan got picked to play rugby for the England deaf team in 2016, he could easily have stopped there.
But he did not: "I realised that I can't be a good athlete doing the one training session a day and going out every night eating food.
"Because of the card I was dealt in Afghanistan, I understand completely differently now that I need to be slightly different."
"I need to be that little bit more tailored, I need to be that little bit more patient and things are not going to come as quickly as it probably would for a person who is able-bodied."
"I completely respect that journey that they're on but my journey is significantly different, and learning that the hard way through the England set-up into now was something that was a tough pill to swallow that I knew I am not going to bounce out on to a pitch and be the best 9 or full-back.
"I actually needed some sort of tailoring, and I had to grow as a person and now I have to make sure I'm out of bed early and getting that extra session in.
"Just tailoring, watching sport, understanding sport - not just on the rugby side but all sports I'm involved in."