Suppose we make a promise that seems fully reasonable. Though later, circumstances arise in which we have to neglect someone in need in order to fulfill that promise.
Maybe a person came to visit and was just leaving in time to fulfill original promise, but they slip and fall ... being injured and in need of medical attention. Do we leave injured person unattended because we made a promise? Of course not.
But, what if we aren't doing what God called us to, because we are busy keeping our word elsewhere, and miss opportunity to meet a spiritual need. Isn't it same thing? The only difference is where wound is located.
Maybe we gave our word and later realized God wasn't calling us to it. Do we ignore what God is calling us to in order to meet previous obligation? Does He come first or second?
In such cases, we have a choice. Is our word God? Is law our God? Is what people think our God? Or, does God's will for us come above all gods?
If we make a promise, only later to realize our error, in order for God to be first - we just might have to eat humble pie. But, therein is a lesson to be learned. The error in making such a promise wasn't God's.