What is the ruling on repeatedly sinning and repenting from it, and what is the way to achieve steadfastness and success in studies?

You must repent to Allah Almighty from watching forbidden things and looking at what is impermissible. Know that Allah is watching you, so beware lest sins committed in solitude invalidate your deeds. Success from Allah is attained by obeying Him and turning towards Him. Therefore, your obedience to Allah and your eagerness to please Him are among the greatest reasons for your excellence in your studies and your success. Hasten to sincere repentance, for its door is open, and "the one who repents from sin is like one who has no sin."