Tell me if this hasn't happened to you before: You open your email inbox and see an email from a company you don't want to hear from or a newsletter that you never read and then you quickly delete the message. Days, weeks, or months pass and then the sender pops up again in your inbox. You again delete. The cycle continues.
Sometimes I forget that I can unsubscribe right there and be done with it forever.
Pay attention to when you're annoyed: you might just find that the time is ripe to unsubscribe.