It turns experiences into thoughts. It separates you from your emotions by changing your priority from experiencing, processing, and accepting your feelings to trying to analyze them. And if you, like me, are prone to mental illness, this can be devastating - because emotions often do not have a reason, especially if your brain has strong natural tendencies.
When you're depressed or anxious, sadness or anxiety form of their own accord. You can feel terrible even when things around you are good, or scared even when there is no danger. And it is very easy to get into the habit of trying to justify these feelings after the fact. When you feel sad and the world around you provides you no reason to, the justification you can give - if you're trying to rationalize your emotions - is that the problem is you, and that is an abyss you can easily find yourself trapped in.
Worse, this habit leads to you being "on the side of" those tendencies. When someone tries to help you to understand that your view of the world is skewed, your habit of justifying and rationalizing makes that feel like an attack on your reason or intelligence. You're not depressed, see, because there's this logical reason you came up with for why you feel bad. And there is always a reason you can give, a justification for why you feel bad, because life always has problems that can be invoked to explain emotions that exist in their own right. But they're not why you're miserable, they're just the reasons you give for why being miserable is rational and right. Healing from that kind of illness requires recognizing your reason and your feelings are different things with different roles, and that to try to rationalize emotion is to make a category error.
Introspection can be good, but introspection must pair with experience, not replace it. You may like such a person because her voice puts you in mind of your mother's, but that origin or association is usually not what is important - the fact that you like them is. You may like the walk because you had a lovely day on it once, but what matters is that the walk brings you joy. The analysis is useful largely when your emotions misguide you ("I keep getting into bad relationships because they draw from X emotional weakness", for example), but even then, you want to feel your feelings even if you do not let them guide your beliefs. When I'm in a depressive episode, I can't not feel bad, but what I can do is recognize that my negative feelings are not truths about the world, so that they do not poison me into a factual belief that things can never improve. When I'm anxious, I can't not feel the fear, but I can recognize that it's not a sign of real danger and that I may need to endure it to make some personal progress. These things aren't about rational understanding of my emotions, they're about a recognition that I do not and cannot control them, only how I respond to them.
I tend to think this sort of thing is a pretty big "original sin" of Anglo-American (or perhaps more generally Protestant?) culture. It arises in a kind of guilt-based virtue ethics, one that I think was originally religious, that tells us that our moral value comes from our impulses and drives, not from what we choose to do with them. It told me, in particular, that my inability to force myself to be more motivated or calm was a personal failing, not a piece of me fundamentally separate from my reason or my virtue. It tells us, as a culture, not to listen to ourselves, not to accept half of what we are, in favor of suppression and repression and self-judgement, and it leaves us as half-people as a result.