Mind (рдорди) is the one thing that makes us happy and makes us sad
Now some people will ask how,so I will explain-:
You are going to the market to buy clothes and a shop comes in the middle, then you say to your mom dad, I have to bring a new mobile and your mom dad refuse and you get sad And you go to the clothing store, 
but there is no previous excitement (like I will wear fresh new clothes from now on,I will wear new clothes in college etc.) and instead of being happy at those clothes shop, you are getting sad and angry at mom dad 
So why are you feeling unhappy, not just for mobiles, it is not the cause of your grief, the only thing is the mind.
The mind is the cause of everyone's sorrow, if you keep doing what the mind says, you will become a slave of the mind and you will remain miserable all your life And yes, listen to this one thing, 
There is no such thing as struggle in the dictionary of the mind, it makes you a dead corpse.
Listen, the heart is better than the mind, because whatever is there in the heart, we cannot easily remove it, the heart is a long term memory, but the mind is a short term memory.
Which only seeks jugaad and laziness, so do not let the mind dominate you, you dominate the mind because on the day you dominate the mind, on that day you conquer the world and yourself.

Thank you very much.