Thompson said the job was relentless and had slowly worn him down over time.
"There are a few things in my life I have to fix up and I want to fix up," the 46-year-old said during his farewell press conference at Skilled Stadium on Monday.
"I've got a lot of loose ends at the moment, so I'm going to go back out there and try to tick all the boxes and knock the jobs over one-by-one."
Thompson admitted a number of his personal relationships have suffered because he's been "totally absorbed" by coaching for the past decade.
"You miss family functions, you miss doing certain things," he said.
"I'm pretty much over the job - the day-to-day relentlessness of it.
"I've got to get back and look after myself a little bit as well and I'm looking forward to that."
Thompson admitted he's been thinking about quitting his job for quite some time.
"I kept it to myself, because if I had have done it six weeks ago then the whole speculation about who was going to replace me, and the goodbyes, would have been a distraction to the team," he said.
"I totally wanted to put every bit of effort into winning the 2010 premiership.
"It didn't happen unfortunately, although we got close, and since then I've just proceeded to do what I've done."
Thompson told Cook last week that he was suffering from burnout and was thinking about stepping down.
But he strangely held off announcing his departure for a number of days.
"In the end, after every season you get tired and you don't think that clearly," Thompson said.
"It's a busy period so I wanted to make sure that when I went away from footy for a little time that I was making the right decision.
"Brian [Cook] encouraged me to do it and I thought it was great advice.
"I did a lot of thinking and still decided to leave."
