Indeed, Jews are not categorized according to scholarship or observance, but, rather, according to their nationhood. Being a Jew establishes one's value. Guilt, which can be healthy since it motivates one to repent, can also be a source of depression. After teshuvah, repentance, one must go on with life - with pride and dignity. One who capitulates to the effects of guilt is falling prey to the yetzer hora, evil inclination, whose goal it is to destroy - regardless of the method.
Depression is as much a conquest as joy in performing evil.
If the yetzer hora compels us to ruminate over our past indiscretions to the point that we are saddened and dispirited, we cannot act constructively - and this is exactly what he wants. He has us doing teshuvah constantly in such a manner that he successfully prevents us from performing mitzvos. This is the yetzer hora speaking to us, encouraging us to false piety. Indeed, such frumkeit can be self- defeating. Regardless of what one has done in the past, he must not despair.