Do what you can; leave the rest to God.
There are so many things in my life that I have no complete control over — all I can do is give it my best. For these things, there’s no point worrying about what happens past that point. Just hope for the best, and know that no matter what, the best will happen.
If what happens isn’t what I wanted, then maybe that’s because I’m short-sighted and can’t see the big picture. In the long term, I must have faith that it will ultimately be what’s best for me.
TL;DR: It’s a subtle balance — knowing when to give it 100%, and when to leave it in the hands of God.
Disclaimer: This is a description of my understanding of the verses in the Quran, and not the real true meaning of the verse. My understanding changes over time – I see many things differently than I did 3 years ago, and my understanding can (nay, it should) evolve with time. Think about how your understanding of the role of parents changes as you grow – first as a kid, then a teenager and later as a parent yourself. Your understanding evolves with time. The true meaning of the verses however, does not. I make absolutely no claims that this is in any way a resemblance of the true meaning of the verses. Instead, this is really just meant to be a record for me – a notebook of sorts, where I think over the meaning verses and try to glean valuable lessons with which I hope to apply to better myself.