Life is the coexistence of all opposite values. Joy and sorrow, pleasure and pain, up and down, hot and cold, here and there, light and darkness, birth and death. All experience is by contrast, and one would be meaningless without the other.
According to Vedanta, there are only two symptoms of enlightenment, just two indications that a transformation is taking place within you toward a higher consciousness. The first symptom is that you stop worrying. Things don't bother you anymore. You become light hearted and full of joy. The second symptom is that you encounter more and more meaningful coincidences in your life, more and more synchronicities. And this accelerates to the point where you actually experience the miraculous.
You are the luminous mystery in which the entire universe with its forms and phenomena arises and subsides. When this realization dawns there is a complete transformation of your personal self into your universal self . . . the complete loss of all fear, including death. You have become a being who radiates love the same way the sun radiates light. You have finally arrived at the place from which your journey began.
There is a light within each of us that can never be diminished or extinguished. It can only be obscured by forgetting who we are.
Not every sky will be blue and not every day is springtime. So on the spiritual path a person learns to find this kind of happiness without needing nice things to happen on the outside. Rather, you find happiness by being who you really are. This isn't mystical. Young children are happy being who they are. The trick is to regain such a state when you are grown and have seen the light and dark sides of life.