On the math module of the Program for International Student Assessment (https://nces.ed.gov/surveys/pisa/) the U.S. places 30th out of 79 countries.
The top 5 countries were all Asian. James Stigler (https://www.psych.ucla.edu/faculty-page/stigler/) concludes from his study that the differences may be due to cultural differences. The strength to keep going for the Eastern Students is the belief that struggles are good rather than bad.

A child will keep asking a parent to keep their promise since the child believes the parent will make good on the promise.

The strength the woman had to keep going to the judge was her belief that he would eventually keep the promise ha made in his oath of office to uphold justice.

Faith is a gift from God, of course Jesus will find it when He returns. He says that we are to USE IT by praying persistently!

There are 3 categories of "stuff" in life: our stuff, others' stuff and God's stuff. And the only one we can really do much about is our stuff. So, when the struggles we are having involve the other 2 categories, give them to God and move on.... Then try not to take them back!

So, "In Life's Struggles, where does our strength come from to keep going?"

Our Strength to keep going is our belief that God keeps His promises and that He hears and answers our prayers in His way and in His time!