How does Muscle work?

I am a veggie kung fu practitioner who has recently been supplementing his diet with Soya isolate protein.

The question is I have noticed good gains and an increase in muscle size as well as tone. If I stop eating it for a few weeks, will I lose the muscle? Even if I continue to train? My thinking was that, I probably would not lose it just not gain any more?

Any advice would be great,

W