Boredom

Its the state where being alone and no one is there to talk with you. Its very disappointing stage that all you want a friend with whom you can just talk and do stuff but you end up as a alone guy with nothing to do kind of a feeling.
Yes this feeling come from time to time but when you feel this you find yourself in a position that no one care about your existence and till this day of your whole life you just being a guy or girl who is not visible to anyone in this planet.
So boredom is really bad for mental stage and for being happy and mentally healthy make friends talk to other, take a walk or do whatever you find interesting just don't let this boredom convert into depression so do it fast. 
Stay safe
Stay strong
Be always happy
At least a smile on the face will work out