There are too many worries in our routine life but if you started to scream and show weariness on each and every one of these worries then, things will get complicated and complex and you will not fit in society.
Anxiety is not a bad feeling all the times instead it can give you energy and hope in some desperate situations but that hope and strength come from controlled anxiety.
There are different reasons behind anxiety getting out of control. It can be a phobia, an emotional situation, an accidental trauma, and any of such other events but once you realize the core problem then, it gets easier to eliminate and address that situation.
The main question here is, is anxiety-disorder a disease or it is just another mental situation. The answer depends upon the state of anxiety because a long term anxiety disorder can lead you to a full-time illness or disease but if you can control it in initial stages then, it can be just another temporary mental situation.