It is a mistake to think that the yetzer hara’s purpose is to merely cause a person to sin; its true goal is to destroy a person completely. Once he tricks someone into sinning, it does not even let him enjoy his act, but rather consumes him with remorse. It is terrifying to think what kind of enemy each of us carry within ourselves. ~ R’ Itzele Petersburger zt”l
When we sin, we must regret it and do teshuvah, but don’t fall for the yetzer hara’s tricks and get you depressed over it.