Besides its own intrinsic benefits, trusting G-d in an intelligent and serious way has two very practical advantages to the parnassa experience. The first is that this trust (bitachon) can serve as an inner guide through life's complexities and turmoil. The second is the tangible sense of contentment, calm and happiness that results.
Either of these could really make a difference at the start of a new career.
Though it's not unreachable, understanding and absorbing bitachon requires a fair amount of work. There really is no substitute for an in-depth study of Sha'ar Bitachon from Chovos Halevavos (along with the review and attention necessary to deeply integrate the concepts into daily life). Nevertheless, here's a very brief (and subjective) overview of the subject (Sha'ar Bitachon can now be read in English online).
A human being who realizes that both his life and success lie in the hands of G-d and that the effort he makes is important (for various secondary reasons), but irrelevant to the results, has bitachon. Let me say that again (using different words) for emphasis: bitachon is the understanding that the things that happen to you are independent of this-worldly causes and effects, but come from G-d. The deeper you know and feel this idea, the closer you are to thinking the way G-d wants you to.
Bitachon, then, is primarily a lesson in man's relationship to G-d. One who makes this principle an integral part of his life is, by definition, more G-dly.
But besides that, as we mentioned, there are bitachon's practical advantages.
Playing a complex game successfully would be next to impossible without knowing the rules.
Imagine sitting down to a chess match against a grand master knowing that your object was to conquer your opponent's king, but having no clue what that entailed? Your opponent, on the other hand, besides knowing the game's basic rules, is also intimately familiar with hundreds or thousands of the best strategies used by his peers and predecessors and can, therefore, use that knowledge to anticipate an opponent's plans and counter them. But you? What chance will you have against a master?
Imagine entering the dangerous and highly competitive field of equity day-trading as a young, untrained individual with nothing more than a laptop computer. You're bound to quickly lose everything you've got because you lack a sense for the complexity of the work and the intelligence of your competition. A business degree from a prestigious university might be somewhat helpful as basic preparation, but even that doesn't approach the value of the solid (and often painful) experience of apprenticeship.
What's our hero missing in these examples? Familiarity with the system. Ignorance might sometimes be bliss, but it's more often devastating.
Now let's watch a young Jewish adult take his first independent steps in G-d's great world. That world runs according to G-d's rules just like chess follows the familiar patterns of its rules and day-trading, its enigmatic path. To do well, you've got to know the way it works. Otherwise, you're simply groping in the dark; you're going to make many tragically wrong decisions.
Ok. What, then, are the rules of bitachon; what are G-d's rules?
By way of example, let me first ask this: If, thanks to G-d, my family's needs are going to be provided to us in any case, why bother working?
Because G-d, in His wisdom, decreed that we must ("By the sweat of your brow will you eat your bread"). Partly, according to the Chovos Halevavos, to test our strength and loyalty to His Torah (how do we act, in both halachic and moral terms, while under stress?).
But, since results aren't connected to effort, how much effort you should invest in, say, a career, will be determined by different considerations. How many hours should I invest pursuing this potential customer? For how many years should I train for a career? How much deep thought should I spare for anticipating all the countless potential problems with this contract or that sale item...intellectual energy that would otherwise be spent on Torah study?
There is, of course, no set answer for these questions, but someone with bitachon at least knows how the question is framed and will understand the general guidelines for developing a solution.
Without bitachon, a dark cloud will forever hover at the very edge of your consciousness: Maybe I didn't do enough to get that job. Maybe I should have dressed differently. Maybe I should spend more time at the office...
Of course you must do "enough" to get that job, you must dress appropriately and treat your professional tasks seriously. However, secure in the knowledge that G-d has the final signing authority on your paychecks (and that He performs a similar service for your next company in case you're fired by this one), you needn't lose any sleep worrying about your financial future.
This security allows you to travel the corporate corridors without feeling the need to compromise your Torah standards in order to please some important manager. It allows you to stand above the temptation to cheat a customer, client (or the government). It allows you to go home at the end of the work day and open up a sefer, content that you've done everything you needed to and hurt no one.
It allows you to be happier.
Can you really make it without this particular employment tool?