If I say I trust you, what does that mean? I think of it has having two dimensions:
1) I trust that you have good intentions toward me.
2) I trust that you have good judgment.
(1) is fairly self-explanatory: I believe that you mean me well.
As for (2): If you don't have good judgment, then I don't believe that you have the capacity to discern what is actually good for me. In that case, your good intentions are not particularly reliable.
But what does trusting someone's judgment mean?
Let's start with what it doesn't mean. When I say, "I trust your judgment," I don't mean that I believe everything you say must be absolutely right. I don't mean that when you talk to me, I forfeit my right and responsibility to think about what you are saying. I don't mean that if I disagree with you, I will assume that I am wrong and you are right and discard my ideas without a second thought.
But when I say "I trust your judgment," I do mean: I believe you are intelligent and rational and well-informed. I believe you have good morals/values/priorities (in whatever area we are talking about; or if I say I trust someone's judgment without any qualification, I mean I believe that person puts God first in their life). I am biased toward believing that your decisions and beliefs are well-founded. If you say A and I believe B, my belief in B is likely to be shaken; I won't just abandon B, but I will question it, and I will operate under the assumption that you have good reason to believe A; I will ask you what you mean by A and why you believe A.
And often when I say I trust someone's judgment, I mean that I am biased toward believing that they are more likely to be right than I am. For instance, I trust my father's judgment. If he were to tell me (heaven forbid) that he thinks I am too young to marry after all, I would be really shaken up, because I am strongly biased toward believing my father is more likely to be right than I am, but I really wouldn't want to believe he was right in this case. I wouldn't immediately conclude that I should cancel the wedding in July, but I would immediately ask him why he thought this, and I would listen very carefully and with the expectation that what he said would be well-founded.
I should note that I have a bad habit of assuming that I am right and people who disagree with me are just wrong and not thinking clearly. I say it's a bad habit because I know it grows out of arrogance on my part, not because I think I have poor judgment (which I don't think). Being aware of this habit helps me deliberately counteract it; but what I really need is not another filter on my thoughts, putting another layer between my mind and my heart. What I need is a change to the way I actually think/feel in the first place. What I need is an attitude of humility.
In some circumstances, I already have the humility that allows me to truly listen without assuming that any point of divergence from what I think must be a divergence from what is correct. The trivial case is where the person I am listening to is an expert and I am not. The significant case, though, is where I trust the person I am listening to. If I respect and trust him, then it is natural for me to set aside the assumption that any point of divergence is him being wrong. If I respect and trust her, then it is easy to learn from her. If I respect and trust her, I can accept correction from her.
On the other hand, if there is no one whose judgment I trust, then there will be no one who can effectively correct me, which is a bad situation to be in. Moreover, there will be no one whose reassurance I trust, because if I'm worried and someone tells me things are going to work out, I won't be able to absorb that comfort because I will assume they are wrong because they are disagreeing with me. Clearly this is maladaptive.
In order to truly live in community, I need to trust. I need to trust people's intentions and at times I also need to trust their judgments. "Submit to one another out of reverence for Christ." Submitting to someone means placing myself in their hands, and it makes a lot more sense in the context of trust. Granted, it's possible to submit to a person without trusting that person, but that requires trusting Christ. In fact, I think that trusting Christ enables trust in other people. Why? There are two major hindrances to me trusting trustworthy people: pride and fear. Fear keeps me from trusting their good intentions; pride keeps me from trusting their judgment. But trust in Christ eliminates fear, because I know that He is taking care of me, and trust in Christ eliminates pride, because I know that God is God and I am not.
Trust is a risk, like love is a risk, like hope is a risk. But we are called to trust and to love and to hope, because they are worthwhile risks. Trust doesn't mean checking my brain at the door; trust means entering into the full range of relationships.