The whole movement of happiness, unhappiness, happiness, unhappiness, could be called unhappiness. You're suffering because your state of mind is in flux, moving back and forth. The ego's happiness is really a form of suffering, because it cannot live without unhappiness.
Eckhart TolleWhen you listen to the voice in your head, listen to it impartially. That is to say, do not judge. You'll soon realize: there is the voice, and here I am listening to it, watching it. This I am realization, this sense of your own presence, is not a thought. It arises from beyond the mind.
Eckhart TolleYou can be very much aware that when you are stressed, it always is a sign you have lost the present moment. So, you can choose to re-enter the present moment.
Eckhart TolleStrictly speaking, "you" cannot become enlightened, because who you take yourself to be is like a ripple in the ocean of consciousness - or a little wave if you're a VIP - and the ripple doesn't become enlightened until it realizes that its ripple-identity is ultimately a misperception, that it is the ocean taking on a fleeting ripple-form.
Eckhart Tolle