It is wrong to break a vow to someone.
Chris feels that Becky's disability is too much for him to handle, but vowed to stay with her in sickness and in health.
Chris wants to feel less burdened by Becky and her illness.
Chris asks Becky if she knows of resources to help spouses of disabled people care for themselves and their loved one better.
Chris leaves Becky, explaining that he can't take care of her anymore and is at his breaking point.
Chris and Becky work together to find resources that help lessen the load that Chris has to bear.
Becky is heartbroken and tells their friends and family that Chris is heartless.