"if then statement" How to stop it?

As the brick touches the grass it emits particles but when it is not hitting grass the particles stop. That is my goal for this script, I have been looking through other scripts and I'm kinda confused how to do this.

So far I have this.

function onTouched(Hit)
if Hit.Name == "Grass" then  
    script.Parent.Touch.Value = true

if script.Parent.Touch.Value == true then
    script.Parent.ParticleEmitter.Enabled = true
end

if script.Parent.Touch.Value == false then
    script.Parent.ParticleEmitter.Enabled = false
end

end 
end 
script.Parent.Touched:connect(onTouched)