One reason my attitudes are so important is that they affect my actions: that is my behavior and words. If I have a pessimistic, defeatist, negative attitude it will be expressed in negative words and behavior. The reality is that I may not be able to control my environment: sickness, alcoholic spouse, teenager on drugs, mother who abandoned me, father who abused me, spouse who is irresponsible, aging parents. etc.   But I am responsible for what I do within my environment. My attitude will greatly influence my behavior.

If you want to know your attitude, look at your words and behavior. If your words are critical, and negative, then you have a negative attitude. If your behavior is designed to hurt or get back at your spouse, then you have a negative attitude. Guarding the attitude is the most powerful thing you can do to affect your behavior.  And, your behavior greatly influences your spouse.