Can planning to commit a forbidden act in the future affect success in studies and be a cause of poor grades?

It is obligatory to avoid the unlawful and not to resolve upon it, for sins have grave consequences. Persistence in sin is not a cause for success. The texts of the Qur'an and Sunnah have indicated the ill-effects of sins, and that they are among the causes of calamities and misfortunes that afflict a person during his life and after his death. Allah Almighty says: "And whatever strikes you of disaster - it is because of what your hands have earned, and He pardons much," and Allah Almighty says: "And We will surely let them taste the nearer punishment short of the greater punishment that perhaps they will return."