I think destiny can be seen in two ways. One is what you say. There's no point in taking agency as the outcome is predetermined anyway.

But there is the other, where you only invoke it in retrospect and never as an excuse for inaction. Your loved one has cancer and you throw a ton of resources at the problem and they still die eventually. Invoking destiny then makes it easier to accept.

This goes a bit along the lines of this prayer:

> God, grant me the serenity to accept the things I cannot change,

> the courage to change the things I can,

> and the wisdom to know the difference.