A doubt is a gray area. Gray is something which is neither white nor black.
Now, how to solve a doubt?
Accept a doubt as either black or white.
See your doubt as white and there is no doubt. See the doubt as black and accept it. Either way, you accept it and move on.
See someone as either honest or dishonest and accept him. Then your mind is quiet. Then you are not in the gray area of doubt. Have conviction: “He is dishonest and yet he is still part of me. I accept him as he is.” That’s it. Finished.
Doubt is an unstable state with footing neither on this shore nor that shore. From there tension arises. One way or the other, take a direction and regain your footing.
Have you noticed that you usually doubt only the things that are positive in your life? Negative things you don’t doubt. You doubt a person’s honesty, and you believe in his dishonesty. When someone is angry with you, you have no doubt about his anger. But when someone says he loves you, a doubt creeps in: Does he really love me? When you are depressed, do you ever think am I really depressed? No, you take your depression as a fact. Yet when you are happy, you doubt: Am I really happy; is this really what I wanted? You doubt that you are capable, but do you ever doubt that you are incapable?
See this tendency to doubt the positive things in your life. Put doubt in its proper place and doubt the doubts.
Doubt the negative and put your trust more in the positive.