Happiness or Sadness is just a bent of the mind.
When a child is born, it is neither happy nor unhappy. It is because its mind is blank, there is nothing inside it. As the child gathers information, experiences and thoughts, his mind is formed and out of that mind emerges feelings of happiness or sadness.
Consider waking up one day with your memory wiped out. You will not be unhappy, neither you will be happy. That’s because you do not have any information or memory inside your head and hence it is impossible for you to experience any feeling whatsoever.
Consider the sun. The sun is always there, it is fixed and there is no such thing as “Sunrise” or “Sunset”. There is no such thing as “Day” or “Night”. It is the earth that revolves which gives you an illusion that the sun has set and the sun is rising.
Same is the case with mind.
It is you who revolve around life that gives you an illusion of happiness or sadness. It is just your mind which revolves around and thinks about “Sunrise”, “Sunset”.
Supreme control over these things can be achieved through mind control. One who has controlled his mind is far away from wordly feelings of happiness and sadness.
Consider watching the earth and the sun from the solar system. Would you see any sunrise? Would you see any sunset? You won’t see anything. You will see a fixed constant source of light.
That light is enlightenment. This is that state of mind when you are not concerned with happiness, sadness, sorrow, pride, glory and other feelings whatsoever. This state is a state of trance wherein the mind is liberated from the vicious circle of happiness and sadness. This is a state of pure consciousness when the mind doesn’t care about happiness or sadness anymore and hence it is liberated (Mukti)