That sentence can be filled with a good number of things, but whatever that thing is you want to have some kind of clarity about it before you commit. But clarity in discerning the will of God is often not a matter of blinding flashes of light and dreams in the night, but more a choice made in real time based on what you know of God and his ways.
We must watch our desires, those of course can make us pray and interpret life for our own ends (see James) but in the end we are called to make choices in context in good faith, and understanding that God is good.
And that is when we make crazy looking commitments because we believe that for God's glory we can be extravagant. That is when we can throw caution to the wind, once we are assured in our own heart (1 John 4) that we see a thing that is otherwise legitimate, and can be used to his glory.
And of course in the end God is not a killjoy, he does slow hardship be he enjoys our reveling in his good gifts, so long as we first enjoy the giver.