Cross your legs, while standing.
Sit down on the floor without touching anything at all, legs still crossed.
Rise again, without touching anything (including the floor).
That's it. Deduct a point out of ten every time you wobble or reach out to touch anything. Apparently 0-3 points and you're in trouble. You can find this on YouTube, and see an athletic young man smilingly sinking, then rising again like Venus from the foam. I suspect he's been practising.
Gentle readers, I tried this. I wobbled, I touched everything in sight, and ended up more or less like an upturned beetle, limbs waving helplessly. According to this test, I'm already dead. I suspect that all over the country, there are other poor souls similarly placed, floundering helplessly on a thousand bedroom floors before trotting off to put their affairs in order.
Do try it and let me know how you get on.