It's not your fault. If you're under fifty and you're reading philosophy and half of it sails right over your head, here's why. It's hard to comprehend the nature of your own mind. You have all these instinctual controls that create emotions, which create sensations, which trigger the secretion of hormones, the heart rate climbs, a different lobe of the brain lights up. You're designed like Doctor Jekyll and Mr. Hyde.
Some people have extreme versions of this. For others it's very subtle. The trick is to detect the different selves you have. One is the relaxed self. The other is the anxiety self. If you sense you're in the anxiety self, your breathing pattern is probably irregular. Start there.