I've been married for more than 30 years. I trust my wife 100% in everything. I don't know how we would still be married if I did not. I know she also trusts me 100%. In fact, I may be unqualified to answer the question, because there has never been a trust issue between me and my wife.
Trust is a very special thing, just like love. If it is lost, I imagine that it can be very difficult to get it back. It is also an act or should I say a verb, not a noun - meaning a noun is something stagnant and never changing. Love, respect and trust are constantly evolving and moving - growing and tested. Therefore, once it is lost, through hard work on both sides it may be able to be revived over a long period of time.
To me, trust is just as important as love and respect. For a relationship to work for me, there must be all three (trust, love and respect). That is the three legged stool of a relationship.