You need to keep it a shape, or a series of shapes that we call layers or clouds. You do that by maintaining air space between branches. The basic rule is to not allow leaves/twigs to grow straight up or straight down from a branch. You want them to arc sideways. You maintain the thickness of a cloud by continuously clipping when you have more than 4 leaves on a twig back to 4. That will induce the plant to put out new buds in the axils of the 4 leaves you left. Over time you build up ramification within the cloud so that you have many twigs in your clouds with 4 leaves at their tips forming the top of the cloud and with fewer leaves deeper in the cloud. Ideally, you can look up from below the cloud and see ramified branches with just a few leaves lower, closer to the branch which is the source of everything in that cloud.
Here is where you start to trim all stems back to 2 or 4 leaves with the intent to begin forming the top side of clouds, ~to your taste.
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Remember, you want to make space by not allowing foliage from one cloud from growing up into the airspace of the cloud above it, and do not allow anything to grow down from the bottom of a cloud and interfere with the airspace of the cloud below, with airspaces like this...
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You want a clear view of the trunk movement and foliage growing from the rear of the tree that adds depth to the over-all view. Main branches do not have foliage growing from them within and inch or two from their origin. The plant fills up the space, you trim to keep the airspace open, just like you said, “so what, I just trim you and keep you healthy?” Yes.