What four letter term am I?

I am sometimes fun and entertaining

About me sometimes, you don't care

I am sometimes sad and depressing

I am sometimes too much to bear

I am sometimes cheerful and joyful

I am sometimes delightful and content

I am sometimes miserable and gloomy

I am sometimes lucky and fortunate

Sometimes people hate me

Sometimes people love me

And I am sometimes what people dread

I am not a person, nor living thing,

but am part of one instead

I am life.