When you embrace silence, solitude, stillness and simplicity you are entering a place of emptiness, a place void of noise, people, activity and business, and complications and clutter. Embracing the absence of those things with which we are all so familiar. You are removing from your life those things that usually fill it up until there is no room for you, the real you, or God, the real God.
In empting you create a vacuum, a void, and physics tells us that nature abhors a vacuum. That means that something rushes in to occupy that space. If you are dabbling in non-Christian spiritual practices, or a synergistic combination of Christian practices and those from other religions, the something that rushes in will not be from God.
When the unclean spirit has gone out of a person, it passes through waterless places seeking rest, but finds none. Then it says, ‘I will return to my house from which I came.’ And when it comes, it finds the house empty, swept, and put in order. Then it goes and brings with it seven other spirits more evil than itself, and they enter and dwell there, and the last state of that person is worse than the first. So also will it be with this evil generation. Matthew 12:43-45
Cast out one demon, get seven in return. God have mercy on the Christian who chooses another path.
But if you are giving yourself over to those things that focus on the Lord Jesus Christ, He will rush in and fill the void. That is why the spiritual disciplines of silence, solitude, stillness and simplicity are said to make room for Him. They are the emptying.
Then comes the infilling. Focusing on Jesus in Silent Contemplative Prayer and Feasting on Him in the Scriptures and the Sacraments, causes the inner void to be full of the Grace and Glory of God.