When you and God are in each other, you and God are in union. But the Lord is infinite and we are like a little drop in the ocean, so how can he possibly enter and dwell in us? Perhaps we can picture that the Lord fills the entire space and we merely blend in perfectly. To achieve that is quite simple. If you can be completely open to the Lord so that there is absolutely no barrier between you and him so that he may enter you freely as he wills, then you are in union with him! You now experience total freedom in God!