From a rational and ideal perspective, it is wise to learn what you want to accomplish in life and what makes you happy before getting involved with someone else, and to thoroughly interview prospective partners for compatibility with your own needs prior to committing to a marriage with them. Partners don't always have this level of self-knowledge and foresight when they get involved with each other, however. Frequently, partners only begin to understand what they can and cannot compromise on after they have married. In this sense then, although conflict may not be avoidable or solvable in some marriages, it may not have been possible to anticipate that it would occur either. Keeping this in mind may help some people who are angry and disappointed by what their partners cannot offer them to also experience a little compassion for their painful situation and the two fragile humans who occupy it.
The great danger of being ambivalent towards whether to remain married is that someone might never resolve their ambivalence but rather live in it for years and years. Feelings of ambivalence towards your marriage that don't resolve over time and efforts to work them through may indicate compatibility problems in the marriage. Spouses in this sort of situation would be wise to seek out marital therapy so as to better clarify whether things can be changed for the positive, or at least made livable. A therapist (discussed in detail in the next section) is an objective third party helper who can serve as a traffic cop to enable previously gridlocked communication to flow better, and who can serve as a teacher who can assist partners in learning more effective ways to sooth themselves and each other, to have better perspective, and to communicate more effectively with one another.
Aside from therapy, we heartily recommend the book, "Too Good to Leave, Too Bad to Stay: A Step-By-Step Guide to Helping You Decide Whether to Stay in or Get Out of Your Relationship", by therapist Mira Kirshenbaum for those people who feel they are unable to resolve their ambivalence towards their marriage. Where most people attempt to break out of ambivalence by weighing pros and cons for staying in a marriage -- a difficult and not very objective process, Ms. Kirshenbaum takes the perspective of a physician diagnosing illness, and offers specific recommendations for staying or leaving a marriage based on whether particular 'symptoms' are present in that marriage. Some symptoms in a marriage, such as abuse, are almost always associated with negative marriage outcomes, for instance, and it is almost always a good idea to leave such marriages even when it is painful to do so. The book is clearly written, compassionate, and provides sensible direction in a situation that can seem hopeless.