In addition to trust, one could also discuss this topic under the heading of ethics, that is to say, the science of how we are to live prudently, happily, and virtuously in the world.
Christ and his Church make a number of absolute claims on the soul: faith absolutely necessary for salvation, absolute acceptance of revealed doctrine, absolute moral perfection, etc.
But how does one really live that life? What is it supposed to look like? What is it supposed to feel like? How does anybody know, especially in this day and age when there are so few living exemplars, and when Traditional Catholics already feel like an endangered species?
It should not be surprising that some people who earnestly set out on the path of Christian perfection develop a siege mentality. If they have accepted literally Christ's call to holiness, then we should assume they're acting in good faith. If there is something incorrect about their approach, it's probably because in their minds they have cathected the absolutizing imperative to the wrong object.
Psychological trauma easily does this to a person, and the devil loves to trouble further already troubled souls. Wrestling against one's sinful tendencies and feelings of guilt can drive one to the brink of despair, for instance. Also it is hardly unheard of for people to compensate for any real or imagined personal inadequacies with an excess of religious devotion. These are just two examples; it would not be difficult to think of many more. And even when such people realize that maybe their lifestyle isn't working out too well for them, they have on their side the explicit teaching of the Church that the number of the elect will be few, that such as who are approved of God will suffer in this life, and that it is necessary to forsake this world for the Kingdom of God. So did many of the saints suffer in loneliness, and aren't we called to be saints?
On the other hand, the mere act of bringing psychology into the discussion raises the equal and opposite danger, i.e. that of believing that the faith, even at its best, is only a primitive form of therapy and has no other function but to smooth over the sharp corners of life. But Catholics are usually well fortified against that error, so much so that the very suggestion that they ought to happier might provoke a determined resolution to remain in misery. It starts the cycle of doubt all over again.
For the record, I do not believe that this description applies to most Traditional Catholics. I do not believe in the myth of the socially awkward Trad. Most of the Trads I know are very well adjusted and happy, especially the young ones. But a lot of them also seem somewhat naïve and I wonder to what degree their faith has really been tested. After all why shouldn't they be happy? They probably grew up in good homes, they had parents who didn't abuse them, who gave them the milk of faith from an early age, who kept them safe from serious sin and its consequences and from the more deranged aspects of the culture. It may be that they got to their present condition of happiness quite easily.
The description applies a fortiori to horribly abused, betrayed, ghetto-extracted melancholic literary converts like me. I can't decide whether I feel more like the Catholic Good Will Hunting or the Catholic Mogli who just stumbled into the man-village. I really do struggle with all of this stuff. But so would, I believe, many people out there in the "mission field," those whom we should be working to convert. They have been damaged by sin and by the culture; and the more damaged they are, the more they will be feeling pain and looking for answers and expecting to get them from the Church.
It is impossible to get to the bottom of doubt by mere thinking, for there is no end to the parenthetical nesting of paranoid premises. This is why ethics is so important. I have actually planned to write a few posts on this topic -- confessions really -- which will hopefully help both me and others.