How can one stop sexually harassing a sister, masturbating, and feeling guilty?

The temptation of women is great and dangerous. Islamic law has forbidden all means of fulfilling desires except through marriage or lawful concubinage. Harassing one's sister is even more forbidden and goes against natural inclination and morals. Merely looking with lust at anyone other than one's wife is forbidden, so what about harassment? Al-Shirbini said: "As for looking with lust, it is absolutely forbidden for anyone looked at, whether a mahram or not, other than one's wife or female slave." Ibn Taymiyyah said: "Just as they (scholars) agreed on the prohibition of looking at a non-mahram woman and mahram women with lust." What is obligatory is sincere repentance by abandoning this evil, feeling remorse, and resolving not to return to it. One must also cut off the causes of temptation by avoiding being alone with one's sister and looking at her 'awrah (private parts). It is necessary to hasten to marriage, strengthen one's connection with Allah, rely on Him, occupy one's time with what is beneficial, associate with righteous people, and supplicate frequently.