Jaromir Jagr -- one of the best NHL players ever -- says he's fortunate to be alive today ... after his car collided with a tram at a high rate of speed.
The Pittsburgh Penguins legend explained the terrifying accident in a post on his social media page Wednesday ... saying it was all his fault.
In his post, which was written in Czech, Jagr said he was trying to cross the road, and ultimately didn't see a tram that was coming at him at "high speed.