What is Paul's constant admonition about the old self or old Adam?
Paul consistently admonishes believers not to yield to old Adam, but to keep him under subjection. He urges them not to give their members as instruments of unrighteousness unto sin. Paul applied this himself, keeping his body under control so it would not become an instrument of unrighteousness.
Les explains that Paul’s constant admonition to believers is not to give in to old Adam but to keep him under subjection. He emphasizes the exercise of the will: the text does not remove choice, but it is a matter of yielding. Believers are told not to yield their members as instruments of unrighteousness unto sin or old Adam. Paul himself practiced this, saying in Corinthians that he kept his body under control lest it become an instrument of unrighteousness. Les adds this does not require becoming a cleric or monk or torturing oneself; the Christian life is a life of joy, responsibility, and freedom, not self-torment.