- Make sure your suspicions are valid: i.e., that you have some evidence that makes you doubt the other person's character.
Think of reasonable alternative explanations that might explain his discrepancies in a positive manner (e.g., maybe he has been secretive because he's planning a surprise party for you). This does not mean that you know this to be true. At this stage of your suspicions you are drawing a mental range. At one end of the range, he or she is deceitful and dishonest -- someone you need to write off. At the other end of the range, he or she is a decent person who is planning a surprise for you or has understandable and rational explanations for the discrepancies. You are trying to identify where this person falls along this range.
Don't accept vague answers to your questions. Rephrase and repeat each question until you get answers that make sense, until you gain clarity. Fine-tune your questions to the specific concerns you have. Don't apologize for asking questions (e.g., `I was just wondering…" `I don't mean to be nosy but..."). Be confident (`I am disturbed by...").
Don't let the other person shift your focus to self-doubt. When people try to get away with something, they become masters at shifting the focus away from themselves and focusing it on the questioner's vulnerabilities. They often try to induce self-doubt and unearned guilt in their victims. (Many politicians are experts at this.) Don't fall into this trap. If you doubt your own mind it will mentally paralyze you. If you believe the motor in your car is not working, you will give up trying to use it. If you think your own motor, your mind, is broken, you may also give up. The result? Depression.
Be aware that if the other person is guilty of doing something underhanded, then he or she has methods to cover this up. What methods? Such people minimize or deny their own behavior. They may try to case you out. They figure out what you want to hear and tell you just that, to throw you off the trail of their deceit. Be one step ahead of them by knowing their typical methods.
Ask yourself how you would answer someone asking you the same question if he found discrepancies in your words or actions and you were innocent. What tone would you use? How would you clarify any misunderstandings? Then compare this to his behavior. Is he behaving as you would behave if you were innocent? Or is he behaving as a deceitful, crafty person would behave?
Don't be afraid of mental effort. The feeling of self-confidence, "I have a right to make sense of my world," and the willingness to clearly think things through earns you a sense of inner confidence and gives you a means to deal with others – it's the best help for anxiety and depression.
When you have doubts about another person's character, you want to hold your own head up high and respect your own mind. Instead of passively drowning in "what-ifs" with no clear answers, you become a fact-finder par excellence. You know you have a right to the truth and you have a right to pursue contradictions in another person's words or behavior until you can make sense of them.
If you have this mindset you will be much less vulnerable to anxiety and self-doubt. You will know that you have a right to make sense of your world, to pursue the truth and to act accordingly. Then even if you find out bad news, that the person you care for (a husband, a child, a friend, a boss) has been deceitful, has drug or alcohol problems, is gambling, etc., you can manage this truth so much better – because you will assess him rather than damn yourself. You will not be swallowed up by self-doubts.