This causes the emotion to ferment underneath that layer, and since it's prevented from venting itself, the person sometimes emotionally deforms more and everything becomes harder to solve.
Part because person is blind to what's happening and has a very powerful defensive layer which prevents everyone (including psychiatrists) reaching from problematic emotions and trying to heal them.
Sounds odd - what exact methods are you talking about?
I don't know the exact names of the methods, but they essentially train to push these bad experiences deeper and pretend that they didn't happen or affect you in the first place.
However, they both happened and affected the person. Pretending not is dangerous akin ignoring a wound with infection.
Every emotion/trauma affects you and these effects manifest somehow. These effects are self-regulated via feedbacks like "I feel X", "I'm not feeling OK", "Hey, this makes me happy" or "Why do I feel like that", etc.
Ignoring an emotion's or secondary effect's presence removes the self regulation circuit hence, allows it to run amok. Since person trained him/herself to ignore these emotions or its manifestations with great effectiveness, wounds grow deeper while practitioner pretends it's OK.
At the last stage, person permanently ignores the problem and pointing to it results in violent responses from the affected person.
I've met with people these symptoms. All of them practiced or was practicing self-affirmation / self validation practices with minimal or no supervision.
Every practice, done mindlessly is dangerous. Including Zen, Yoga and others.