We have been taught to believe trust is a commodity to be earned by others. Once they have passed certain tests, then we feel safe to extend our trust. I would like to entertain the idea that trust can be a verb, rather than a noun. It's a choice you make and says much more about you than it does the person to whom you are extending that trust.
When you are involved in a relationship and you say you trust that person, it is more than a noun. It's not just a thing you extend to a person like a gift--it is followed up with behaviors--things you do and things you don't do.
When you trust someone, you know he or she will do the right thing. You know they have their affairs (no pun intended) under control. They are faithful and loyal. You don't need constant reassurance of this--you just know.
What you don't do is constantly grill a person about where he or she is and with whom he or she is spending time. You don't have him or her followed looking for proof of infidelity. You don't snoop around in his or her personal belongings or private places. You trust that he or she can be trusted.
Trusting has so much more to do with who you are as a person than it does with who your partner is. When you are secure in yourself and know that you are worthy to receive love, then it is natural to trust.