I have recently answered a question on Quora and thought It could be a good topic to include the answer here.
Here it is:

There is a reason, yet you are not aware of it.

The reason for getting anxious might not be actually caused by the present situation (hence you see no reason for getting anxious) but by the association there is in your unconscious mind to something that happened in the past.

Let me give you an example:

I’m afraid of spiders. I’m consciously aware of the fact they are harmless, creatures, scared of me more that I should be of them (at least where I live). They don’t mean any harm and just go about their business and there is no reason for me to feel so afraid.

Yet I get very strong reaction, feelings that seem out of proportion.

You see, my mum was afraid of most of the insects her entire life. When I was small child I remember playing by the lake, where my faily had been chilling, having a bonfire, good food, most likey some vodka and generally good time…

I also remember a sudden wave of utter terror piercing through my body, when my mum got into panic/hysteria about some kind of insect. It was utterly terrifying experience, because as a small children we totally depend on our parents and experiencing their fear/danger etc has very strong impact on our psyche/body/emotional state… well on everything.

I have been accidently taught to have such strong reactions. You could say that the fear I experience is not the fear of the spider in the NOW but the feelings of utter terror I experienced as a small child.

Additionally: When we are children we tend to store strong feelings, traumas in the body. More precisely in the muscle system. We do that as our underdeveloped nervous system can’t process them yet. These feelings/emotions/energy, gets stuck in our bodies, over time causing chronic muscle tensions, holding patterns.

Until we express these, we might keep experiencing emotions, feelings like anxiety, anger, sadness for “no apparent reason”.

When you experience these feelings, scan your body. How does it feel? Are you contracting any muscles that you are not even been aware of?

Maybe you tense your neck?
Maybe your belly?
Clenching your jaw?
How is your breathing? Deep? Shallow?

Try to pay attention to these things.

If you do have muscle tension that you do not control (you relax your shoulders, and the moment you’re back to reading/watching they’re back being tense) then look at Bioenergetic Therapy/Exercises.

They DO help… :)