Why time is so complicated?

I look at a watch, see that seconds hand moving continuously and only beg to wonder, how does time run continuously and why don't we have a way to stop it?

According to Newton's first law, anything moving in a particular direction will keep moving in the same direction till an external force is applied to it. This works for almost everything but there is no force that can stop the continuous movement of time. Maybe what we perceive as time may not be what nature thinks of as time. We use numbers on our watch faces and use days and Years to determine how much time it has taken for an event. For nature, time maybe non-existant and we have just made it a very big deal. So why make it a big deal?

Humans have the ability to process death and we fear it. That's one reason why we are always worried about the amount of time we have to live on this planet. This also drives us to do enjoyable things over boring activities because it gives you more happiness in that short span of life. Time is so important for us because we have so many things to do in so less time. We humans have deadlines which always makes you think of time. If you compare humans to the nature of Earth, you realise that the things you are doing aren't contributing to the cycle of nature as much as making your life better. Everythig else in nature contributes to the cycle of nature during its entire life span. This maybe a reason for why time doesnt matter to nature. 

The next thing that intrigues me is the relativity theory that says that time changes when we move to other parts of the universe. Even an astronaut on the ISS for 6 months is 0.0007 seconds younger when he/she comes back to Earth. I dont understand this. How can our body clock change according to our surroundings? The activities we do don't change in any way. The clock on your wrist would still run at the same pace. So theoretically speaking you should have the same life span that you would have on Earth. But thats not the case according to Einstein. This theory is beyond my understanding.   

This is why the topic of this post is 'Why is time so complicated?'. Its beyond my understanding but the moment humans are able to control time, Physics would have failed as the entire subject would have been a big lie.

Thanks for reading!