All things need their opposite in order for us to see them and recognise them. Something can only exist with nothing. Fear is the opposite to love. If we haven’t experienced fear we can not experience love and so on.
Dark has to be there in order for light to exist.
Everything has it’s Yin and Yang.
Life changes from one opposite to the other. Ups and downs, pleasure and pain. When we attach our fulfilment to the ups, then we suffer from the down, we don’t want those moments, we deny and resist them and only seek the next up.
Once we accept that no state is without its opposite and do not seek only the one state, often pleasure, then there can be peace within.
All states are temporary and they all have an opposite in order to exist.