All who recite Parshas Haman every day are guaranteed that their livelihood will not decrease. (Yerushalmi Brachos)
“It is insufficient to merely recite it, rather one must focus upon it…so that one will believe that his entire livelihood is attained through Hashgacha Pratis, as the Pasuk states, ‘He who had gathered a lot had no excess, and he who had gathered little had no deficiency.’ (Shemos 16:18) This shows that additional Hishtadlus produces no benefit at all.” (Mishnah Berurah 1:13)
One may ask: What is the comparison? Regarding the Manna, Hashem said explicitly how much each person was to get. As the Pasuk states, “This is what Hashem has commanded: Gather as much of it as each of you requires to eat, an Omer to a person for as many of you as there are; each of you shall fetch for those in his tent.” (Shemos 16:16) This being so, it is readily understood why “he who had gathered a lot had no excess, and he who had gathered little had no deficiency.” This being so, how will these Pesukim reinforce within us the knowledge that regarding our own livelihood as well that greater hishtadlus produces no benefit at all?
The answer is that in reality, just as the amount of Manna everyone received was preordained, so too is the exact amount we will earn each year, as the Gemara states, “A person’s entire livelihood – all that he is destined to earn – is allocated to him – such and such an amount he will earn this year – during the period from Rosh Hashanah to Yom Kippur.” (Beitzah 16a – with Rashi) As long as we fulfill our basic hishtadlus, just as one had to go out to collect the Manna, the outcome of any additional hishtadlus will be just as by the Manna, “He who had gathered a lot had no excess.”
How much more of our lives will we waste attempting to stuff extra Manna into our jar?!