But let's ignore the physics and imagine that, one day, the planet's gravity turned off, and suddenly there was no force of gravity on planet Earth. This would turn out to be a pretty bad day. We depend on gravity to hold so many things down -- cars, people, furniture, pencils and papers on your desk, and so on. Everything not stuck in place would suddenly have no reason to stay down, it would start floating. But it's not just furniture and the like that would start to float. Two of the more important things held on the ground by gravity are the atmosphere and the water in the oceans, lakes and rivers. Without gravity, the air in the atmosphere has no reason to hang around, and it would immediately leap into space. This is the problem the moon has -- the moon doesn't have enough gravity to keep an atmosphere around it, so it's in a near vacuum. Without an atmosphere, any living thing would die immediately and anything liquid would boil away into space.
In other words, no one would last long if the planet didn't have gravity.
If gravity were to suddenly double, It would be almost as bad, because everything would be twice as heavy. There would be big problems with anything structural. Houses, bridges, skyscrapers, table legs, support columns and so on are all sized for normal gravity. Most structures would collapse fairly quickly if you doubled the load on them. Trees and plants would have problems. Power lines would have problems. The air pressure would double and that would have a big effect on the weather.
What this answer shows you is just how integral gravity is to our world. We can’t live without it, and we can't afford to have it change. It is one of the true constants in our lives!