No matter how bright the sky, some dark clouds will exist.
This simply means that challenges aren’t unusual. Whatsoever one is passing through now can still be tackled. You have one or two situations bothering your mind doesn’t mean that others haven’t witnessed such.
No matter how highly placed you might be, don’t be overconfident that you have no challenge to tackle ahead. This proverb is preaching on vigilance and preparedness for no man no what might come next.