The saying that promise is a debt is as popular as our various local foods, however few people pay attention to the weight this statement has to God and humanity.
It is better not to make vows/promises than making them and not fulfilling them(Eccl5:5). God expects us to pay all our vows (Numbers 30:1-2 AMP:And Moses said to the heads or leaders of the tribes of Israel. This is the thing which the Lord has commanded: vs2 if a man vows a vow to the Lord or swears an oath to bind himself by a pledge, he shall not break and profane his word; he shall do according to all that proceeds out of his mouth.)
So, we as Christians should be a good example by being slow to promise and hasty to fulfil them when made.
Nevertheless, when you make some promises and situations will not permit you to fulfil it, a reconciliation should be made with the person / people with whom the promise was made.
He bought famine upon the land of Israel for 3 consecutive years because Saul broke the promise made to Gibeonites who were the descendants of the Amorites (who have lived among the Israelites since the time of Joshua because the Israelite made a covenant not to kill them)
Remember, God values promises.