The air surrounding our Earth gives to all the objects on it (and of course on us with you) with the same force as the pound guitar per square centimetre.
It's a very high pressure: it comes out, one square metre of the surface, gives the force that produces a load of ten tons! But we don't notice this pressure, we do our business, we learn, work, entertain, without thinking about the enormous atmospheric pressure we're experiencing. The whole point is that the external atmospheric pressure is equal to the exact pressure that exists within us (and within all living organisms).
Here are a few air pressure experiments.

A water fox in a glass

Put the water in the glass to the edge. Cover a glass of hard paper and stick to the paper with the palm, quickly turn the glass to the top of the bottom. Now get the palm. The water from the glass won't spill.
Atmospheric air pressure on paper is greater than water pressure on it.
That's why the boom doesn't fall off.
But just in case you do all this over the pelvis, because with a slight dislocation of the paperwork and a lack of experience at first time, water can be poured.