I read somewhere that you should only keep things in your life that are beautiful, useful, or that bring you joy. I live by this. In my mind, if it doesn't fit into at least one of these categories, it must go. Holding onto something that you don't love or use simply because it was given to you makes no sense to me. A cluttered home makes a cluttered mind.
If you apply this to your daily consumerism, you'll find that you buy a lot less of the things that are quasi-disposable. Instead, you will wait and buy things that you truly love when they become available to you.
This applies to the garden as well. Don't be afraid to edit when appropriate. Just because it is green and growing does not mean that it has earned the right to take up valuable garden real estate. If there is a shrub or plant that seems out of place or is not attractive, you will notice it and hate it every time you see it. As long as the plant will be composted and replaced with another plant, you can remove it without a twinge of guilt.
Remember, your landscape plants should be beautiful, useful and bring you joy.