Bible is: "Whatsoever thy hand findeth to do, do it with thy might."
And keep on doing it--persist--persist--persist. Again the Bible:
"Seest thou a man diligent in his business? he shall stand before
kings." Do not fear hard knocks. They are no sign that you will not
finally win the battle. Indeed, ability to endure in silence is one of
the best evidences that you will finally prevail.

Yes, put yourself into your work--and put all of yourself into your
work. Having done that, be content with your effort--do not fret. If
all you do yields the fruit you hope for, do not fret while that fruit
is ripening. On the other hand, if your labor comes to nothing, still
do not fret. A like fate has fallen upon uncounted millions before you
and will come to unnumbered myriads after you. If you have done your
best you have done better than the man who has done more than you but
who has not done his best.

And so, whatever the outcome, start out with this rule and keep it to
the end. For nothing wastes your powers so much as apprehension. The
hardest work, if done with common sense, is after all a tonic. But
fear lest that work will not yield you as much as you wish is a sort
of irritating cocaine of character, numbing and deadening all of your
powers and at the same time lashing your mind and nerves with the
knotted thongs of unhappiness. Besides, fretting is so trivial, so
little, so commonplace. Fail if you must, but do not be contemptible.

He who worries not only poisons the very fountains of his own strength
but arouses in the world's attitude toward him a sort of sneering
pity. So the very first thing that I have to suggest to you is that
you should _be a man_ in all your doings and throughout your whole
career.