Proverbs 26:2 (ESV): 2 Like a sparrow in its flitting, like a swallow in its flying, a curse that is causeless does not alight.

Proverbs 26:2 (NLT): 2 Like a fluttering sparrow or a darting swallow, an undeserved curse will not land on its intended victim.

I am just gonna go over some information out of the book linked below.

Blessing or Curse: You Can Choose by Derek Prince https://a.co/d/7wWcZpu 

I will focus on chapter 11 Authority Figures and chapter 12 Self-Imposed Curses. Below are direct or condensed passages out of these chapters. 

For curses by Authority Figures we will look at our biblical example from Genesis 31, Context: Jacob, his wives Leah and Rachel, two concubines and his eleven children departed from his Uncle Laban to return to the land of Canaan. Laban caught up to Jacob and accused him of stealing his household god. Jacob did not know that it was Rachel who stole the idol. So to protest his innocence he spoke the following curse "If you find anyone who has your gods, he shall not live" (Genesis 31:32). The fact that Jacob did not realize that his words were directed against Rachel did not prevent the curse from taking effect. Shortly afterward, in giving birth to her second son, Rachel died in labor (Genesis 35:16-19). Such is the authority of a husband, either to bless or to curse! (Page 123)

Lets talk about some real life examples. There are some in the book, but I'll just give some of ones I notice reoccur by observing people: 

1. Family members telling parents "oh just wait, you're just getting pay back for how you were".
2. Teachers uttering curses over their students. "They're bad", "They just won't get it"....
3. Parents cursing their own children (Pro-choice mothers saying "Well, I have a daughter, I want her to have a choice if she gets raped". "You're gonna be gay, acting like that" by dad's."
4. I had an older stranger tell me "Oh, your son will be trouble when he's older". Comments like that seem innocent, but you never know who Satan is using to curse you, or your children. Both me and my children rebuke any such comments. 

Let's talk about Self-Imposed Curses:

Our Bible example comes from the Gospel of Mark. Mark 14:66-72 records how, in the court of the high priest, Peter three times denied that he was a disciple of Jesus. To enforce his third denial, he actually "began to curse and swear". In other words, he invoked a curse on himself. 
Three days later, at the empty tomb, the angels told the women, "Go, tell His disciples - and Peter - that He is going before you into Galilee" (Mark 16:7). Peter was no longer reckoned as being one of the disciples. By his own words he had forfeited his standing as a disciple of Jesus. 
Later, John 21:15-17 records how, by the Sea of Galilee, Jesus graciously opened the way for Peter to regain his standing as a disciple. He asked Peter three times, "Do you love Me?" Peter answered each time in the affirmative, but he was grieved that Jesus put the question three times. He did not realize that Jesus was leading him in this way to revoke his previous denials. On this basis, he was reinstated as a disciple. 

1. Repent
2. Revoke
3. Replace

We must acknowledge that we have made a wrong confession and repent of it. We must revoke it - that is, we must unsay, or cancel, whatever we said that was wrong. We must replace our previous wrong confession with the right one. 

These are some examples of Self-Imposed Curses I have overheard:

• "I'll be damned." 
• "I am just waiting for the deployment curse to set in."
• "I'm dead."
• "I wish this house would just burn to the ground."

There are a lot more I could list but I think people get the gist.

A little side note on blessings: 
Context: Genesis 27, Jacob and Esau fighting over Isaac's blessing "On the contrary, all through the Bible, the blessing of a father is considered second in importance only to that of God Himself" Quote by Derek Prince. So if you're a dad, bless your children!

I will also post pages 142 and 143 below to give some more insight on potential curses.