What is to be done about repeatedly falling into sin after repentance, while having the desire for righteousness but being currently unable to marry?

A Muslim must not engage in relationships based on free mixing and seclusion between non-mahram (definition) men and women, as this is forbidden behavior. He must promptly initiate sincere repentance, which entails: abandoning sins, regretting past actions, and having a firm resolve not to return to them. He must also adopt the means that aid in steadfastness, including: associating with righteous people, shunning everything that leads to disobedience, fasting, which curbs desire, and immediately severing ties with the girl.