Being critical of oneself does not seem like it would warrant attention, but the affects of such activity can prove catastrophic to someones mental clarity.
Another way to word it is, self-condemnation. In practical terms we would liken it to having another person in our minds, tinkering with our cognitions and calling us the worst words they can think of. For a moment, think back to the last time someone used a certain words with you and as a result you were hurt by it. This example is the same product self-criticism will produce. Furthermore, it will be a frequent occurrence and in some cases, the hurtful words may be in some sort of cognitive loop, repeating daily, hourly, and out of control.
These are the reproaches the person has brought against themselves. Much of the criticism, similar to [http://hoplitelyfe.com/low-self-regard/], is directed at features in themselves that the person values.
In addition, there is a tendency to blame themselves for everything.
Most of the blame has no logical basis yet continues to solidify into a presumed truth as the distortion gains more ground in the persons cognitions; and thus, their reality.