Tawbah And Despair
It is to be decided by God in the light of his absolute knowledge that the person was really sincere but weak in his determination or fake and self deceived. It is for the salvation of man to make sincere repentance and firm abstinence for the sins. When he abstain from the major sins his minor sins are forgiven. But if he commits major sins his minor sins too are added to make his case worse.