The 32-year-old has revealed the magnitude of the decision he has been made, but how his long term health and family must come first.
"It has been a huge mental and emotional decision to come to," said Horsman. "It was a decision between my health and my family and the game I love.
"It has been really, really difficult. I reached the point when I went to see a surgeon and he told me if I carried on playing it would hit my long term health.
"When you have got three children and a wife, and as much as I would love to carry on playing, it's important for me to still live my life in a relatively active way.
"If I was to carry on playing rugby I could jeopardise my health and potentially the life I am giving my family, I had to make them my priority.
"As tough as it has been since pre-season started, and I know it's only going to get tougher, I know that I have made the right decision."
Horsman has been forced to overcome some major obstacles in his life and twice successful battled against cancer.
And he acknowledges the next will be leaving his playing days behind that will leave a void in his life.
"Rugby has been a huge part of my life for 12 years. I have been completely institutionalised in a way by it and have absolutely loved it.
"I would do it for nothing, I would pay to do it, so I have been very fortunate with the things I have achieved and the people I have met and teams I have played for, particularly Worcester and Wales.
"There have been fantastic moments, but when you push your body to the limit, which I have always tried to do, you can get a freak injury in training and that can end your career, that is hugely disappointing.
"Ultimately, it is a choice between trying to play another season and get through six months and potentially cause my neck all sorts of long term damage. It is just unfortunate that now is the time to call it a day.
"I have had almost 20 operations from rugby and having had cancer twice I have been through it - sometimes the biggest and hardest decision is to say enough is enough."
Horsman leaves the game after a glittering career for club and country that has seen him play for Wales on 14 occasions and also take part in the 2007 Rugby World Cup.
"I'm hugely pleased by what I have achieved in the game," he said. "I'm happy that I can say that, even though my career has been cut short with the setbacks and illnesses and cancer, I have still managed to achieve things that I never thought I would be able to achieve.
"I'm 32-years-old and have a lovely family and beautiful wife, I'm pleased that I have got what I have outside of rugby and that the sport has given me the opportunity for fantastic life experience and to lead the life I have."
Horsman is now weighing up his future and revealed he is keen to still play a part at Sixways Stadium and given a ringing endorsement on the future at Warriors.
"The club have indicated that they want me to stay involved in some capacity and it's something I would like," he added.
"I would love to keep my links with Worcester Warriors, it is a club close to my heart and out of all the clubs I have played for it has made a massive impression on me.
"The supporters, Cecil Duckworth and the coaches and players have been fantastic to me. But, ultimately, it is a decision I have had to make with my family.
"It's disappointing that I have had to retire with the Warriors not where I would like them to be. I want the club to be higher up the Guinness Premiership table and in the top European competitions. But I'm sure they will be there, if not this season, then the one after.
"If there is some sort of part I can play in that I would be delighted. I am very passionate about the club, the supporters, the players and anything I can do to make this club a success I will do."