“”Every complete tzaddik is a baal teshuva. If he is a genuine tzaddik he is constantly making a cheshbon hanefesh and doing teshuva.”
So, how do you learn Pshat in that Gemara?”
That a person needs to constantly be doing teshuva. A person cannot tell himself that he did enough mitzvos yesterday or that he has reached his potential. Everyday of his life he needs to work to be a better person, because even if he is not doing aveiros, he could still be striving higher.