A short YouTube excerpt from Dr. Don Wood explaining why anxiety arises: the mind uses past negative experiences as a resource when predicting future situations, so prior hurts (for example, from a previous relationship) lead the mind to project risk into new situations and generate anxiety. He emphasizes that anxiety is a protective response—not evidence that something is wrong with you.
Chapters
If you have a lot of experience in the past with things that have been hurtful, your mind is trying to protect you. So let me give you an example. You're going to get into a new relationship and now the anxiety is just going through the roof. Why is that happening? Because of a previous experience where you got into a relationship but you got hurt. So anxiety is bringing to your attention something that could happen. However, that anxiety is going to affect the way you live your life if you're always worried about something that could happen that hasn't happened. So anxiety is dealing with things that have happened before and your mind is projecting that same problem into the future. So if you've got a book of experiences that have all been very negative for you and that's the resource that your mind uses when it thinks about something moving forward, can you see why anxiety would show up? There's nothing wrong with you and nothing wrong with your mind because you have anxiety.