If you think about it, serenity is a very subjective thing. I have known people who find serenity at the top of a mountain, and others who find their peace while screaming down a ski slope at sixty miles an hour. I've also have heard the old saying "The only serenity you find on top of a mountain, is the serenity you bring with you." I suppose that this is somewhat true, but I would offer this caveat. You don't have to bring the serenity with you. You merely have to bring the ability to access that through which you can experience serenity in the current moment with you.
If I trudge up a mountain, and it is a physically exhausting climb, and I am hungry and thirsty...I probably won't be feeling to serene...yet. I would need to recover a bit, relax, and reset. Once I have found my footing I can then access my practice and set my intention, relax, bring my attention into the NOW, and be in the dynamic moment.
It is in that dynamic moment that I will find my serenity and Truth.
I can understand how screaming down a ski slope at a high rate of speed can clear your mind of all egoic thinking. However, this is not my idea of serenity. Adrenaline junkies will tell you that there is no greater peace than being in the moment. While I agree with that premise completely, I have a hard time reaching it when I feel in great danger. This method would hold me back from being able to access that serenity at any and all times. I can always find time to practice during my day. Driving, walking, eating, working, etc. are all conducive to practicing presence in the current moment. If I had to put myself in danger in order to clear my mind of egoic thinking it would not make for a very practical practice.
We each have our own way of making practice work if we pursue it with all of our intention. You have to find what works for you. Try something. If you like it...use it. If you don't...let it slide down the mountain at sixty miles an hour and have a seat next to me.