He also said he was available for selection and hoped to play against Fremantle on Saturday night.
Watch Ben Cousins' press conference
The Richmond veteran was admitted to hospital on Monday after an adverse reaction to a sleeping pill meant he could not be woken. He was kept in intensive care overnight but was released on Tuesday.
Cousins spoke to the media on Wednesday morning but did not elaborate on the type of sleeping tablet he was administered, saying it was a matter between him and his doctor.
"It's not illegal or anything untoward. It's something that's been prescribed to me with a fair bit of thought process ... it was just probably an error of my judgment," he said.
"It was probably scarier for the people around me. I was lucky my girlfriend was there."
Cousins said he would not be taking the sleeping pills again, but denied a culture of abuse regarding caffeine tablets and sleeping pills existed in the AFL.
He admitted that there would be speculation about the episode given his history of drug abuse and said his offer to submit to drug tests was motivated by his desire to prove he was totally clean of illicit drugs.
Cousins, a premiership player with West Coast, has endured lean times since being selected by Richmond with the last pick in the 2009 NAB AFL Pre-Season Draft.
He battled injury throughout his first season for his new club, which saw the Tigers win the wooden spoon in 2009.
But four wins from the last five games has taken Richmond off the bottom of the AFL ladder. Cousins played in all of those matches making a solid, if not spectacular, contribution to the Tigers' form turnaround.
Cousins said he would be disappointed if the curtain was drawn on his career at the end of the 2010 season but would leave the game without bitterness.
"I've got eight games of footy that I'm looking forward to and I'm hoping to play good footy and justify my existence," he said.
"I'll sit down with the coaches and see what they have in store.
"I've had a great time at Richmond ... It's been an amazing club to be involved in; they've given me an opportunity to get my life back on track."
A former captain of the Eagles, Cousins was sacked by the club in October 2007 after continued issues with drug abuse. The AFL Commission banned him for one year for bringing the game into disrepute.
After completing drug rehabilitation and agreeing to submit to testing, the Commission lifted Cousins' ban in 2009, paving the way for his selection by Richmond.
