That’s one other good reason we are told to pray without ceasing, in fact. The Lord knows there will be times when we don’t have anything on our minds. It’s easy to lay awake in the middle of the night and think. But, not only should you cast all your cares on Jesus, you should also keep your mind focused on Him. Never let your mind be idle. When it’s at rest, that’s when those bad things can enter into your heart.
This is why meditation is bad unless it is focusing on God. It’s easy to forget that there are bad spirits in the world, too.
Eastern meditation, the bad kind, comes from a worldview that says everything is good. But, it’s not. God made everything, but He is not in everything. He has given us free choice. And, He gave His angels that same freedom. Some of them rebelled, though, and now work against Him. The chief of those is the devil.