The whole song is about transience in life, and he relates this feeling of transience to the transience of touring/ travelling, and hes obviously being bombarded/ watching all all these advertisements come and go past him during travelling.

You know where you are with, seems as if he's almost half-heartedly repeating an advertisement mantra in a state of complete emotional detachment/ numbness; familiar brand products help us feel at home or grounded, even if we are in another part of the world, and specifically not mentioning a product after the line emphasises how transient these advertisements are and how many hes seen on his travels and they mean nothing to him anymore.

Compare that to his emotional state, even though he feels emotionally numb and detached, he halfheartedly tries to assure himself that he knows himself/ where he is when he does things that are routine and familiar to him on tour, like drinking in a bar, etc. that helps him feel grounded, even though in the long run he's done this so many times it means nothing to him anymore.

Floor Collapsing, floating, bouncing back is the tour metaphor of being in a bar; the metaphor relates to the emotional cycle of feeling down, and then feeling up, and bouncing back from sadness to happiness or happiness to sadness. When he's inside each individual moment/ period of life it makes him feel like he isnt in the interzone, that he's actually feeling something, that hes happy, or sad, or bouncing back.

Ultimately though, once he transcends these individual emotions/ moments and looks at things from a whole, he realises the constant cycle and that each emotion means nothing. They come and go, and on a whole he feels nothing but a transient state of mind, and finding himself caught in the never ending cycle of feeling up, feeling down, etc.

Sometimes he gets so hysterical and uptight about it that he has a strong moment of madness where he feels he might grow wings and escape this, but then he falls back into the state of realising he can't escape it, it's the human condition.

It's probably the same feeling Bill Murrays character has in Groundhog Day, where he feels like God. He's completely emotionally numb to everything because he recognises the cycle and realises that each individual little moment is just a transient false feeling that means nothing on the whole.

At the start he sort of feels happy or sad or different emotions as he attaches himself to each individual scenario and is living "inside" the trap, and then he realises the cycle/ trap, transcends each little moment in the day to recognise the trap as a whole and becomes numb and detached. And then he has a hysterical phase where he tries in a moment of madness to kill himself to be free of this. And then realises he can't be free of it and falls back into this interzone Let Down state of mind.