Love, joy, and peace are deep states of being or rather three aspects of the state of inner connectedness with being. As such, they have no opposite. This is because they arise from beyond the mind. Emotions, on the other hand, being part of the dualistic mind, are subject to the law of opposites. This simply means that you cannot have good without bad. So in the unenlightened, mind-identified condition, what is sometimes wrongly called joy is the usually short lived pleasure side of the continuously alternating pain/pleasure cycle. Pleasure is always derived from something outside you, whereas joy arises from within. The very thing that gives you pleasure today will give you pain tomorrow, or it will leave you, so its absence will give you pain. And what is often referred to as love may be pleasurable and exciting for a while, but it is an addictive clinging, and extremely needy condition that can turn into its opposite at the flick of a switch. Many love relationships, after the initial euphoria has passed, actually oscillate between love and hate, affection and attack.
Real love doesn’t make you suffer. How could it? It doesn’t suddenly turn into hate, nor does real joy turn into pain. Even before you are enlightened, before you have freed yourself from your mind, you may get glimpse of true joy, true love, or of a deep inner peace, still but vibrantly alive. These are aspects of your true nature, which is usually obscured by the mind. Even within a normal addictive relationship, there can be moments when the presence of something more genuine, something incorruptible, can be felt. But they will only be glimpses, soon to be covered up again through mind interference. It may then seem that you had something very precious and lost it, or your mind may convince you that it was all an illusion anyways. The truth is that it wasn’t an illusion, and you cannot lose it. It is part of your natural state, which can be obscured but can never be destroyed by the mind. Even when the sky is heavily overcast, the sun hasn’t disappeared . It’s still there on the other side of the clouds.
Reference : The Power of Now. Eckhart Tolle.