Based on the writings of Rav Chaim Cohen, the Chalban, Tallelei Chaim, Sefer Bereishis, P. 554. Even though there is a requirement to try, we must remember that everything still depends on a brachah (blessing) from above. Bitachon is a person's entire way of looking at life. Why reliance on Hashem is not the same as a partnership (or marriage) where each party only takes care of "their" half. Hashem not only takes care of "part" of my life. "Ein od milvado" means that He is involved in everything, and constantly. Different aspects of choosing a way to make a living - talents, capabilities, phsycial or mental strength, inclination, etc. Animals - naturally (by Hashem) designed to feed themselves. The contradiction between wanting a life-style that cannot be afforded by the profession we are interested in pursuing (or have talent for) - it things get a littel bit rough, don't through in the towel.