From A Commentary on the Doctrine and Covenants by Stephen E. Robinson and H. Dean Garrett, p.19-20, regarding D&C 42:22 (I emphasized a couple of things I particularly liked in bold):
...In the law of the Church, all marital conditions other than loving "thy wife [or husband] with all thy heart" are prohibited. Men or women who have allowed themselves to fall out of love with faithful, loving spouses are in violation of the law and are under condemnation. Although biological attraction can happen spontaneously, maintaining a long-term, loving relationship in marriage usually does not. It is a goal that must be chosen and diligently pursued, a conscious decision for which husbands and wives may be held accountable. To ignore one's spouse or the relationship that exists between husband and wife is a sin. Sometimes the spouse does not respond to the expression of love, in which case the offending spouse will receive the blame, but for as long as a marriage lasts, true Saints are obligated to love their spouses and maintain a warm and loving relationship to the degree a spouse will allow.
Since exaltation requires that man and wife become one not just in the "bonds of matrimony" but in heart, mind, and spirit, they must love one another. If they fail to do this, exaltation must be denied the offender who will not love his or her faithful spouse. Our covenant obligation to be one with our spouse is second only to our obligation to become one with the Lord.