cjamison said:
In what ways would 'meditation' or breathing exercises be considered 'sinful'? Cultivating a deeper relationship with yourself and caring for yourself, which meditation is meant to develop, is a good thing. Or not?
It's not the exercise that's sinful, but meditation becomes an area of temptation when we believe that there is something that we can do that will make us "more godly" as a personal achievement. For example, reading scripture with understanding is good, but considering "understanding" to be our achievement rather than a gift given by the Lord to us and through His word is self deception and pride at work in our hearts.
Also consider that Eastern techniques for meditation focus on breathing with the intent of clearing the mind (of worldly thoughts). Some forms of meditation use words and images as mantras which may stimulate the imagination (and God's word says that our imagination is only evil all of the time) and may make us susceptible to suggestion by external forces, spiritual or otherwise: This sort of meditation utilizes a kind of autohypnosis which is all the more powerful when generated by our own thoughts. Do you want your behavior modified by external forces?
I prefer internal suggestions in the form of the promptings and teaching of the Holy Spirit, but you can only experience this if you've been born again.
Jesus' voice is the only voice that I want to receive and we train ourselves to hear that voice by reading His word and meditating upon His revealed will, with prayer and seeking His desire rather than our own. That takes some level of discipline on our part, but if we don't make time for Him, He'll make the time for us and sometimes in less than pleasant circumstance. In all things we need to find wisdom. Everything that we do has some consequence, so its far better to seek what's best rather than what we simply believe to be good, and only the Lord knows what is best for us in the long run.
I hope that my response isn't obtuse and is in some way helpful to your own understanding.