Sometimes you can't recognize what happens around you even though the whole world knows about your partner's regular patterns towards you in the scope of making you a victim of his/her mistakes. And when you realize you feel utterly devastated and deeply hurt because of your blind trust, intense faith, and negligence under the name of love. Even though when people around you keep poking you to notice your partner's distracting moves, you wouldn't be in a position to believe them.
Of course, a relationship completely depends on the factor of trust but believing your partner in every possible way could also hurt you psychologically and emotionally. You need to observe a few behavioral patterns of your partner that bother your mental peace and emotional stability. You don't have to compromise your common sense to find what's wrong and what's right just because you are deeply in love with someone. If not, you become a scapegoat and should sacrifice your whole personality in the eyes of the world. Hence, you need to be aware of your partner's way of dealing with everything in and around your romantic relationship!
If your partner gets benefitted all the time regardless of his/her/their blunders by manipulating you and if you feel that your partner is trying to cook up some story to conceal the facts, you need to confront it by expressing your doubtfulness regarding any particular matter.
And if your partner is true to you, instead of questioning you back, he will express his feelings or she may give you a proper closure to make you understand but if your partner overreacts and tries to backfire you by opting for the factor of doubtfulness against you by spilling a statement question, "Don't you believe me"? Or "Are you doubting me"? Then you must think about the whole situation.