Psychologists call this the "psychological moment." You can tell a depressed friend 100 times that they should go for a walk and they'll ignore you. Then for some reason the 101st time it sinks in, they go for a walk and lo, they feel better. Psychological moment applies to all sorts of changes. Telling your abused friend that they should take the kids and leave, telling your aging dad that it's time he gives up his driver's license, asking your husband to stop interrupting you. 100 times they ignore it, 101st time it clicks. Everything is timing.