I remember with crystal clarity only a few moments in my life - almost all were outdoors - waking up in a hammock just as dawn cracked, floating in Windermere as dusk set in, amazing memories. My children's births I also remember but the amazement and awe is overlaid with stress and worry - so yes, get outside if you want your heart to relax.
I one travelled to Ushaia Argentina and then simply picked a random hill to climb. It was about 3000ft and had snow on top in summer. I was under a lot of stress because my wife was in town and had an injured back. I contemplated if I should go all the way up (there were no paths) but decided I will probably never have the opportunity again. When I finally made it up I could see into a valley without any human development. It was one of the best moments of my life. Since this day I go out into nature more often and also spend a couple of nights outside alone. I always come back clearheaded.