Aikido, as O-sensei taught it, is about protection of all things, yourself and the attacker. That does not mean there can be no pain involved, for as O-sensei said- "Even pain is a manifestation of love." For instance- there is a video of O-sensei performing shihonage on a police officer on the roof of a building. However, the cop almost spins out of it! My instructor (Roy Suenaka) suggests in his Book Aikido Kyohan (plug plug) that O-sensei could have wiped him out, but they were on a roof, with no mat, doing a technique on a civilian with little to no falling experience. As Suenaka sensei says: "It's not bad technique, it's the loving protection of all things..."
Something to think about,