Already translated, but I am very confused...

I am currently doing a self-study on translation and I am reading a daily devotional book and its Spanish translation. There is one translation of a sentence that really has me stumped. I was wondering if someone here could help me understand. Pay attention to the part that is italicized.

Original: "When the Lord calls you to come across the water, step out with confidence and joy. And never glance away from Him for even a moment. You will not prevail by measuring the waves or grow strong by gauging the wind. Attempting to survey the danger may actually cause you to fall before it..."

Translation of that sentence: No porque midas las olas por eso has de prevalecer, no porque escudrines el viento por eso has de fortalecerte.

Note: My laptop will not allow me to add the "~" over the "n" in "escudrines"

Is this a good Spanish translation? I have a feeling that it is, although my mind reads that version: There is no reason to measure the waves because you must prevail, no reason to gauge the wind because you will grow strong. Which seems to convey a message opposite of the original.

I swear, I have been pondering on this for days! I really need help!

The explanation here is the use of the subjunctive, it denies something.
Se utiliza el subjuntivo cuando se niega una causa con porque, es decir, cuando se usa no porque
'Estudia español porque le gusta, no porque lo necesite en su trabajo.'
In your example, it is not possible it measure the waves or gauge the wind, therefor, it is saying that it’s not because you do such or such an action that you shall have such or such result.

You can download the Doulos SIl font which will enable you to write the "~" form this page: http://scripts.sil.org/cms/scripts/p...osSIL_download

Wow, I understand now, thank you.