You are a small planet in the universe and don't have enough mass to survive. With time, you're losing mass, therefore you have to gain mass, while eat other planets. The rule is the bigger mass wins, so you have to care of bigger masses. Two abilities will help you to stay alive:

First you can split your mass and gain velocity and second you can feed other planets. To see the size of other planets, you can project your planets to the positions where they will land after split.