The Maimonides in the laws of teshuvah chapter two halacha two writes the steps of teshuva (based off verses in the prophets) which break up into four stages.
Firstly, leaving the sin which this means that one ceases to sin, removes it from his mind (thought) ,
Secondly, he is to decide whole heartedly that he will not sin anymore,
Thirdly , he is to regret and feel bad about the past so much so that g-d can testify that he will not return to this sin and not do this (or in truth any sin against g-d) ,
Fourthly, one is to confess to actually utter what he sinned and proclaim his decision that he will not return to sin
(chassidus explains that every sin has a body and a soul and when does teshuvah he is to fix the body and soul of the sin , by feeling bad – remorse he atones the soul of the sin but the body of the sin is only fixed when one actually utters the viduy – confession).