How we change what others think, feel, believe and do
Get rid of your unhappiness. Push it out. Throw it away.
Have a good cry. Wail and grieve. Sob away your hurt.
If you have friends who will allow it (ask permission first) have a good rant at them. If you do not or do not want to do this, then find a place alone where you can rail and shout about the world. Swear a lot. Hit something soft like a pillow.
If you can afford it, a therapist or counsellor can help you expunge your deeper darkness.
You can also do something active and physical, like playing a contact sport, though beware of anger that may hurt others. Or do something physical alone, like digging the garden or chopping wood (carefully!).
If you do things that make you unhappy, stop doing them. Find happier things to do. Though first think about what the underlying cause is. If you are unhappy with all the jobs you have ever done, then maybe there is some inner cause. The same goes for friends. Leave those who do not make you happy, but remember your own part in making friendship work or not.
For relieving short-term stress, you can use simple techniques such as taking a break or just one deep, slow breath.
It is strange, but many of us seem happy to hold onto our unhappiness. Much of the time it is because we are not unhappy enough to do anything about it.
The first step towards purging deep unhappiness is realizing that you are not as happy as you could be and that there are things that may be hidden, even from you. Meditation or therapy can help, and seeking help is a big step forward.