An answer from the Rebbe to someone who wrote about his hardships in Parnassah:
אולי החסיר לאחרונה – בשיעורי בתורה וכיו”ב בעניני מצות.
אשר זהו בטח הסיבה הפנימית (ובמילא גם האמתית) להעדר ההטבה בהנ”ל.
Perhaps you have caused a deficiency lately – in your Torah studies and the like in matters of Mitzvos.
This is, most certainly, the inner reason (and therefore — also the true reason) to the lack of improvement in your abovementioned financial hardships. ■