This is a very common problem all around the world. Probably the biggest misconception out there concerning bonsai - JUNIPERS BELONG OUTDOORS, just like PINE TREES, SPRUCE TREES, MAPLE TREES and a long list of other hardy and temperate trees. They just can not live a healthy vigorous life inside a house.
With the wonderful world of internet knowledge available at your fingertips anyone can and should learn some of the very basic horticultural aspects of growing trees if they want to be keepers of little trees in little pots. They are living trees and trees need certain things that we can provide them. Making bonsai from them is secondary to keeping them healthy.