Step-by-step explanation:
When we are forced to endure a situation that requires us to stretch ourselves, we discover how far we can stretch. When I was doing school, I faced significant academic challenges that I won't go into here. Nevertheless, I discovered that my strength allowed me to push not only past the benchmark but beyond it, as I graduated early a decorated member of NHS and valedictorian. I strove for these things, and I know my strength academically is far greater than I thought it was, especially as I am now pursuing an engineering degree and taking the course equivalent of two full-time jobs per term.
I got there by being forced to recognize where I was weak so that I could patch those areas and become stronger. That is what this quote means.