the question I can't answer

how does it all begin?

where does it end?

this is the story of my life.

i don't remember how I came to this world. the only thing I know by the time I can think properly I already am in this world.

In this world, I am facing with many obstacles, and I also facing with many happiness.

And now I realised I have been given time to spend in this world.

And with this time i can spend it with many things.

And once the time has gone out,

All that's left is my knowledge and what I have done in this world.

And slowly all the remains of me slowly forgotten.

Until the end of the world.

I know what i will think by the end of that time.

What i have spend in my life?