First, (we are here) to ask this question, and second, to find an answer to it! Many live their whole life without even asking the question, ‘Why am I here?’
Wake up, ask this question, and pursue to get an answer. Do not be in a hurry for the answer. The answer falls into your lap at the right time, so keep asking.
No books will answer this question, because this is the question of ‘life’. Your life itself is an answer.
Every day, if you ask, ‘Why am I here?’ then all the unnecessary things fall off, and the right things come up. However, before asking the question (why am I here), ask, ‘What can I do for this world, before I exit? Anyway, I am here!’
This may be a better question to soothe you in those moments when you feel nothing is enjoyable, or everything is meaningless.
When you feel sad, depressed, suicidal or unhappy, at that moment you should say, ‘Let me stop thinking about myself. Let me see what I can do here. Anyway, one day I must go. Before I go, let me do something good here. Where am I needed? Who needs me? Where can I help out?’
These questions can bring some intermittent relief in between.
So do some service (seva). When you do some seva, you make others happy, that vibration of bringing comfort to others souls will bring you merit that will help you realize who you really are.