Is what happened—the separation from the girl after nine years, and the change in feelings towards her due to despair over work and lack of resources, followed by intense regret after her engagement to another—divine decree (qadaa’ wa qadar) or a personal mistake for which one must bear the consequences, and how can one distinguish between the two? And is repentance after associating with those who despair considered sincere repentance (tawbah nasooh)?

It is highly unlikely that a relationship between a man and a woman who are not mahram (definition) could last nine years without transgressions, and this necessitates repentance to Allah. You should not marry this woman, even if you promised her, and you must completely forget her after her engagement. Marry if you are able; otherwise, occupy yourself with what benefits you and beware of the steps of Satan. There is no contradiction between what happened to her being by Allah's decree and it being a mistake on your part, for your mistake is from Allah's decree, as everything is by decree. Perhaps a servant is deprived of marriage due to his sins and transgressions that distance him from Allah if he does not repent from them. Allah Almighty said: "And whoever turns away from My remembrance - indeed, he will have a constricted life." Obedience brings sustenance and goodness, as Allah Almighty said: "And if only the people of the cities had believed and feared Allah, We would have opened upon them blessings from the heaven and the earth."