Anxiety is a normal human feeling.
Anxiety is what you feel when you are faced with uncertainty. When you do not know what is going on or what you should do about it, you react with a feeling of anxiety.
What makes anxiety pass? Resolving the ambiguity. Figuring it out. What's happening or what to do about it. Then the feeling is gone, and you are relieved. You may still have work to do or a problem that needs to be fixed, but the anxiety about it is finished.
When people suffer from depression they often also feel anxiety and spend too much time worrying, which increases their depression. The parts of their brain that are involved in that normal reaction to ambiguity are working overtime. And the thinking brain, low on energy due to depression, cannot stop that worry train. When they worry too much and can't exert enough control, then the feeling of anxiety persists beyond any situation that includes some uncertainty. In fact, the anxious feeling can be present before any uncertainty. Then it creates the nagging sense in your gut that something is wrong, so your helpful brain, the one that wants an explanation for every feeling you have, goes on a search to figure out what might be the source of that anxiety.
Because the natural response to anxiety is to try and figure out what to do, you may start to think over all the possible reasons you could feel worried, and you will inevitably find one. When you are depressed your brain generates too many negative thoughts and cannot effectively shove them aside. You can get stuck in a loop of worrying one worry after another. However, because real problems are not the reason you have the sensation of anxiety, you either think and rethink in an effort to get relief or you move on to yet another worry. Thus: rumination and "serial worrying", hallmarks of anxiety fuel depression.
There is a lot you can do about this. You can use your brain to change your brain. Here are 2 ideas to start out:
1. If it is a real problem, you will not fail to notice it: In your "thinking brain" you can assess if the problem you are worrying about is a real problem. If it is not a real problem (perhaps just a potential problem) you can decide "not to believe everything you think". This is a conscious, determined choice to disbelieve the sensation of anxiety that feels so real. In its place you put an intentional more positive thought: You are competent to know when you have problems that need attention. Then you move your thoughts along to something more positive.
2. Stop and Interrupt: You will also have to use your thinking brain to stop and interrupt the worrying. As they say in the 12 Step programs, this process is simple, but it isn't easy. You must plan what you prefer to think about on a daily basis and then when the unnecessary worry pipes up, you stop, interrupt yourself, and replace it with the preferred thought. The hard part is doing this every time an anxious feeling creeps in or a worry pops into your head.
There are many ways to use your brain to change the brain. Learning various methods and putting them into place starts a process that is the first step to lifelong change. You might need some outside help to achieve this persistence in the face of such distress, but controlling anxiety is doable over time. As you get more control of anxiety, your depression will diminish too.
Author of The 10 Best-Ever Anxiety Management Techniques