If you happened to fall from the height of a skyscraper - this is the same as if you suddenly found yourself in the middle of the ocean, and there was not a soul for miles around, or if you came to life in the coffin of a burning crematorium furnace - you are already dead, although you are still moving and breathing. The only difference is that death will come instantly and painlessly. I can only advise you to remember all the brightest that was in life, and not think about that which was not bright in it and will never be, and even more so, not to think about dark deeds. There is no need to be sad before death, it is sad in itself.
If you fall from an airplane that has fallen apart in flight, you can only wave your hands in the hope of flying up to some debris and, if possible, surround yourself with the largest number of them, making a nucleus this heap near you as soft as possible, from armchairs, for example. A person by himself develops a maximum of 40 m / s when falling, and in such a heap this indicator will not change much. You can survive. There were cases: wikipedia.org wikipedia.org
And try not to suffocate: at an altitude of many kilometers there is almost nothing to breathe. How - in an extreme case, the body will figure out itself.