Watch what you say. That is a lesson that can be learned from Jephthah. Who is Jephthah you ask? He was a judge of Israel. You can find his story in Judges 11-12. Interesting story. I won't go into detail on his life (you can read it for yourself). But the one thing that stands out to me as I read about his time as a judge is the vow he made before he went out to fight the Ammonites. He said, "If you (the Lord) will give the Ammonites into my hand, then whatever comes out form the doors of my house to meet me when I return in peace from the Ammonites shall be the Lord's, and I will offer it up for a burnt offering." (Judges 11:30-31 ESV)
There are two things I see: 1) Jephthah was influenced by the pagan culture in which he lived. The act of offering up a burnt offering was a part of the culture of the people of Israel. The tragedy of the vow is found in that it was his daughter who came out of the house to meet him. The Lord was appalled by the pagan practice of offering up people as burnt offerings. That was what took place in the worship of Molech and Baal. It was seen as an abomination. Yet, Jephthah does just that. Why would he imagine that what the Lord saw as an abomination would be acceptable to the Lord? (You could ask that about various things going on in our society today as well.) Human sacrifice was and is wrong.
2) Jephthah spoke too quickly. He made a vow without even thinking about what he was saying. He spoke rashly in the heat of the moment. This is like King Herod when his daughter danced for him at the party. It cost John the Baptist his head. Here it cost Jephthah's daughter her life. He made a vow when he should have just been asking for the Lord's guidance.
Be careful what you say. You can't put the words back in your mouth. And when they come back to you, they will be bitter. Think before you speak. Let your words be according to the will of the Lord and not according to the desire of your sinful heart. In order to know that your words are in accord with the Lord's will, you need to spend time in that Word of God.
Jephthah spoke rashly and quickly. Have you done something similar? If so, instead of further it on and causing more problems, admit you spoke wrong, ask for forgiveness and then change the way you talk. The Lord is willing to forgive. He will also guide you in how you live each day.