Harrison Ford as Henry Turner in Regarding Henry (1991)
There is apparently a part of the brain that causes a person to be a dick. When a robber (John Leguizamo) shoots unscrupulous asshole attorney and philandering husband Henry Turner in the chest and head while he's trying to buy some late-night smokes, the frontal lobe trauma and brain damage caused by oxygen deprivation turn him into a far more sympathetic mute cripple amnesiac.
As Henry regains his powers of speech and movement, his new simpleminded appreciation for everything endears him to his wife, daughter, and pretty much everyone but his mistress and other former fellow d-bags, who he abandons for a life filled with love. So, you see, there's no relationship therapy that can compare to a good braining.