Wales lock Jake Ball admits he returned too quickly after suffering concussion in 2018, and has warned other players not to make the same mistake.
Ball, 28, was this week named in Wales' squad for the Rugby World Cup.
But he missed much of last season with injuries, including a concussion which he returned from after two weeks.
"I wanted to play, didn't want to let anyone down... and probably should never have done that because I wasn't quite right," said Ball.
"Even though I passed all my tests and that, I think I still knew."
Scarlets forward Ball was concussed in a tackle by Glasgow prop Alex Allen - who was sent off - on 1 December and returned to play in a European Champions Cup match against Ulster on 14 December.
He believes his condition contributed to him receiving a shoulder injury in a derby match against Ospreys on 22 December, which sidelined him for a more than a month and ruled him out of much of Wales' 2019 Six Nations Grand Slam campaign.
"I had a nasty head knock which I tried to sort of rush back from," he explained.
"Probably I wasn't completely honest and that led to another injury from that and there are some things probably that I would have changed along the way."
Ball said the symptoms of his condition were more obvious to other people than him, and warned other players to be aware of any changes after taking blows to the head.
"I'd never really had a bad concussion before... and I didn't really realise what was going on," he told the BBC Scrum V podcast.
"I had a bit of trouble with my memory and stuff like that, I wasn't myself. To be honest it was probably more my wife who said to me 'you know, you're not quite right'.
"Don't ignore anything, however big or small. If you're not right just bring it up - obviously you are at high risk of picking up other injuries if you do play with it so it's just not worth it."
After an injury-disrupted season Ball says he was "desperate" to be part of Warren Gatland's 31-man squad which flies to Japan next week and is keen to do well for his family.
"They want to come and watch, and that for me is a big driving factor... making them proud is a huge factor for me."