There are some reasons to why you should not feel sad.

Common reasons :

1.Spoils good mood.
2.Highly contagious.
3.Weakens your mind.

Primary reasons :

1.We don’t have time to be sad.
2.It can’t solve problems.
3.It can never solve problems !

Never be sad of failure.
Never be sad of what you had lost.
Never be sad of what went wrong.
Never be sad of someone who left you.
Forget your happy-sad cycle. 

Never think that being sad will soon bring happiness. Happiness is not the opposite of sadness. Someone has misguided people by this cycle. 

It is not an antonym.
It is not part of a cycle.
But a state of mind.
You are happy, if you believe you are happy.
Stay happy.

– Pradeep