Some kisses, especially in close up, are so tender: the slightly open mouths are silently talking a language of closeness and merging, of soft welcoming, of greeting and needing and gratitude. To simultaneously being wanted, wanting, and also disappearing into sensation and boundlessness. Just looking at them evokes desire, surrender, and tears. Transcendence.
Others are stolen, rushed, imposed (even if mutually), shattering the calm with urgency and the complexity of the awareness of sinning, of the simultaneous guilt and thrill of doing something that mother (not to mention the spouse!) would disapprove of. The lips are bruising one another, banging into teeth; the hands are desperately clutching. Each is possessing the other for what both know can only be a few moments. There will be torment later.
(Image = "Lovers in a Bistro, 1932-33" by Brassai; http://www.masters-of-photography.com/B/brassai/brassai_lovers_in_bistro_full.html)