Tom says, "Poetry is not a turning loose of emotion, but an escape from emotion..." This statement sums up the relationship of Tom and Viv as well as the journey of the film. Tom and Viv live in a relationship that is emotionally volatile, yet Tom has a distinct ability to restrain his emotions with Viv. We begin to understand that he is channeling all of his emotion into his poetry, and his statement--made earlier--appears to be about how he is not turning loose his emotions in his life as he saves them for his poetry.
The issue becomes that all that he feels for his wife becomes so bottled up that he never visits her before her death in 1947. He puts her away in an asylum, yet he tells Berty that she is with him everyday, and we see a serious tone within him. It is as if he is saying that he knows she is well enough to be released, but he doesn't do so. And, he doesn't visit her because he would see that she is stable. Her stability does not lend itself to his creating poetry as he believes he writes best when he is sick. Thus, he is sick knowing that she is well enough to be home, yet he keeps her locked away in order to keep the fervency of creation inside of him. This is a tale of loyalty to art above all, even their marriage. As this kind of loyalty is itself the marriage they've agreed to have.
