I am unsure how to translate the fail part of this phrase "If you try, you may fail, if you don't try, you will fail." Can I use echwe? "Si ou eseye, ou ka echwe, si ou pa eseye ou pwal echwe."

Echwe is the right word. You got it right.

"If you try, you may fail, if you don't try, you will fail."

Si ou eseye, ou ka echwe, si ou pa esye, ou pral echwe.

or

Si ou eseye, ou ka echwe, si ou pa eseye, w'ap echwe.

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