Time and again we should lift our eyes away from the mundane. The nature of the mundane is that it just occupies you and swallows you completely. Small things can occupy your mind and your time. Simple things such as cooking, shopping, washing clothes, ironing, all these trivial small things eat up most of your time, and sometimes they drown you and keep you so occupied that you have very little time to look at something which is beyond the material existence.
So the wise people, while doing all of this, will time and again taken their attention away from the mundane and shift their attention towards the subtle. This can happen during sun rise and sun set. When the sun is rising just gaze at the rising sun. At that moment, there is a shift in the universe from night to day, and in that shift the mind also easily shifts from the mundane to something ethereal, to something beyond. The world of the Gods is inches away from us, not very far.
So if you lift your eyes from the mundane and look at the sunrise, the mind lifts away from the mundane.
This sun is rising from so many millenniums, still its charm and its newness has never diminished. The sunrise creates more alertness and wakefulness in you, while the sunset is more relaxing and romantic with the birds singing. It just takes you to a dream world, and the mantras start coming up in you. Prayer happens spontaneously. Instead of talking about the mundane things, connect with nature. It uplifts you. That is why it is called sandhya because the dawn and dusk are the best time to relieve ourselves from the mundane and to get a foothold in ethereal, in the subtle, and in the most beautiful realm of the creation.
Similarly on full moon day, when you look at the moon your breath becomes musical. Looking at the moon, the prana in you becomes musical and life becomes harmonious. That is why all spiritual practices are connected with the sun and the moon. Buddha got enlightened on a full moon day. Guru Poornima happens on a full moon. Full moon meditation is very well know. So the moon is also very connected to spiritual practices. You can say that these meditations are more compelling.