A relationship can only stand when there's trust, and if at a point it starts to shake, misunderstanding finds its way inside and soon, destroys all that was built over many years.
Trust is having confidence or reliance on someone or something.
Trust isn't built in a day, it takes years of knowledge about someone to trust them with certain behavior or fidelity. But unfortunately, one wrong move can damage one's reputation and leave the relationship hanging on a thin pole.
Trust is important in every relationship. It gives each of the partners some level of confidence in one another. A relationship should be built on trust for it to stand. Trust then becomes the ingredient that spies a relationship up and saves the partners from thoughts triggered by doubt.
A lot of people have found themselves in a position where trusting people is difficult, and this is because of their past experiences that hurt. If someone whom I had once trusted gave me reasons to doubt him on different occasions, it gets to a point where I no longer trust the words they say or have confidence in their fidelity.
It's not easy to trust someone again once they've proven to be unreliable, but there's always ways one can reconsider and that's if they truly realize what they did was wrong and admit it, feel genuinely sorry about what they did, and notice certain changes over time. Even with that, I'll still put my guard but give them a chance to prove they've changed.