A little SciFi vision

Every planet in the universe, that actually is a planet and not the remnant of a cataclysm, has a sun in its center. That is, because the matter of each such living planet manifested through the energy gate we recognize as sun and the plasma it brought forth. Depending on each suns strength and environment, it would allow the various sizes of planets, while the matter it spewed into existence hardened into a hull around it over time. There are, however, suns of different quality, with the strongest of them too powerful to allow for matter to coagulate and therefore not forming a planet, but trapping planets in orbits around them, creating solar systems. All suns are gates and all gates lead to the same source, transcending the concept of location, but not that of time.
All throughout the cosmos, civilizations exist, who have understood this and have managed to link with these suns, forming gateways through the source to any place in existence. While most only conquered travels from planet to planet, few have overcome the power of solar system centers, enabling them to travel with massive armadas at once from one system to another. It takes enormous ambition to do so, and those who dare are rarely benign.
Very few planets have the right conditions to support life on their outside, while virtually all have life inside, facing the central sun. On these special planets, though, life on the outside represents great challenges, but has the rare privilege to see all the stars in the sky at night. It also has the privilege of seeing what comes through the stars and can respond in time, should ever a threat appear. And these threats do appear, cutting short the development of civilizations within, if they can't react in time.
Earth is such a special planet and because of it, it has one of the most ancient civilizations there are, but of the benign kind.
Time and time again, humans on the outside, after having chosen this kind of exile, become weary of the challenges and gradually turn ambitious. Time and time again, they rediscover their roots on the inside and wish to become a greater force of the universe, wishing to forge a gate through the solar center and become conquerors themselves. Time and time again, they have to get subdued and reminded of the real reason and purpose of material existence and who or what they truly are.

"I see the great sun every day, feel its force upon my skin, see its might, bringing everything to life around me and scorching without mercy that, which we have rejected, reminding us of its power by freezing that which it has neglected."- verse of an ancient song.

This shall become the story of such cycle, when humanity grew weary again.