Help... U2 lyrics... do not understand

Either or both about dying and being buried or breaking up with a woman, which is a kind of death.

Confusing, I agree. My offering A person coming to self awareness after following/being influenced by another person, a leader perhaps. Realization that the other person is not worth following, and finds a foundation in "the ground to kneel upon." the other person's act of misleading, "smoke machine", is represented by his/her "smile"

I believe it concerns an old flame who has come back into the life of the singer after many years of absence. Seeing her again powerfully evokes passions the singer hasn't felt since youth. The singer, however, wants to avoid falling in love with her again, in part perhaps because he or she (or both) are already committed to someone else. "I don't want to see you smile" = I can't stand to see you smile because it will draw me to you again.
"It started, lighthearted, it won't be easy like you said": A common beginning to a reconnection with a former lover is the claim that "we'll just be friends again." The singer, however, already feels the magnetic pull of a force other than gravity (i.e., romantic desire) and warns his old flame that it will be difficult to maintain an innocent friendship. "I will live again, you will live again.": I think the lines have a dual meaning. One, the singer is rebuffing, gently, his former lover's advances by assuring her (and himself) that they don't need to be together again in order to feel the youthful passion they once felt. They can feel alive apart from one another.
Two, it may include a reference to reincarnation. Passionate lost loves who are driven to reunite by a heart connection that never waned over the years may wonder if they were lovers in previous lives. Such a history would explain the intensity and duration of their passion in this life. The singer may be counseling his old lover that, while circumstances may have separated them in this life, they may be able to try again in their next lives. "God knows it, knows me, knows me, knows me": "God knows me" is something you say when you refer one of your personality traits, particularly to one that is a character flaw. We've reached an emotional crescendo at this point in the song. It is the sound of a person struggling to control themselves, to control a darker side of themselves. "Save it again, burnt out blind, the smoke machine is yours not mine" - obviously smoke machine refers to some kind of deception. The specific deception here is self-deception. The old flame is lying to herself if she thinks she can reconnect with the singer and not be swept away by the ensuing passions. I was inclined to view the lyrics through a "lost lover" lens because of previous songs with lyrics written by Bono that document an obsessive love affair that ultimately ended. I suspect that these songs, along with Smile, are highly autobiographical. I speculate that they reflect an affair Bono may have had with a women (not his wife) in the mid 80's (reflected in "With or Without You", Joshua Tree; "All I want is you", Rattle and Hum; and "Night and Day" a song featuring an extremely dark, intense, obsessive love affair). The end of this illicit relationship is ruminated on in Achtung Baby's "Who's going to ride your wild horses" and "So Cruel." Bono reminisces about her in "Wild Honey" (which also has a reincarnation theme). And finally, in "Smile", he is confronted with her when she attempts to reconnect with him again.