Taking a drug that permanently damages your heart, lungs or even liver, often isn’t.
Dangerous sports need risk analysis, and failing to do that increases the chance of an irreversible result.
Having kids is not reversible - if you change your mind six months in, you don’t get the same outcomes for the rest of your life as if you had never had them in the first place. It’s not consequence-free, whatever route you take from there.
You might be ok with downsides and risks associated with a decision when you make, but it doesn’t mean the decision is reversible. Some decisions (“should I move my family to a foreign country?”), have greater consequences and less reversibility than others (“shall I have an extra slice of toast this morning?”).
I also want to stress something I wish I’d grasped when I was younger: when you’re 25 you get to experiment more with the big stuff than you do when you’re 35 or 45. And that time passes fast. At 45 you will not have the same degrees of consequence-free reversible decision making you had when you were 25.
But there are still decisions you make at 25 that will stick with you forever, no matter what. Choose your friends and lifestyle carefully.