We pray to Hashem for sustenance. This is an indication that we realize that sustenance comes from Hashem. We receive His sustenance through the various media that He employs on our behalf. We, of course, think that how we earn a living is our choice, when, in fact, it is totally from Hashem Who guides and directs us. The choices we make coincide with what Hashem wants us to do. In other words, when we do not achieve success at one position, it means that we should move on to another. Quite possibly, Hashem does not want us to earn our livelihood this way.
Hashem has the wherewithal to provide for everyone, and, in fact, He does. What we fail to understand is that Hashem provides for those who study His Torah. One should never make the foolish mistake of thinking that, by studying Torah, he is wasting time that could be spent earning a living. On the contrary, it is only through his spiritual endeavor that he merits material sustenance.
In his commentary to the Siddur, the Kol Bo observes that the prayer for sustenance begins with a bais and ends with a mem. The Torah Sheh’b’Ksav, Written Law, begins with a bais, while the Torah Sheh’Baal Peh, Oral Law, begins with a mem. A person who studies the Written Law that begins with bais and studies the Oral Law that begins with mem will merit Hashem’s sustenance. The pursuit of Torah learning will not impede our ability to generate a livelihood. On the contrary, Hashem provides for those who learn Torah.