Very simply, the things which last eternally will give you eternal happiness. That which is transient, changeable, that which will die, that which will recede in time, will not give you lasting happiness.
The tendency of the senses is to go outward all the times. Sri Krishna says, ‘Your senses are always busy in going out to the objective world. And when you can’t obtain those objects then your mind obsesses over them. This outward driven tendency of your senses is stealing your wisdom.’
Every human being seeks happiness. Everybody wants to feel joy inside. We want to smile, laugh and dance. When we are happy, colours of the trees seem brighter, sky looks vaster and you are filled with so much energy that you could scale a mountain. We wish to be happy but because we are under a veil of māyā (an illusion) we mistake fleeting happiness for eternal bliss - and this is the source of all our miseries....