I agree. Your quote from James 3:17 sums it up. That which is peaceful, loving comes from God. Plain and simple. That which is fearful, anxious, despair, comes from human fears and insecurities.
I like the meditation classes at the local Buddhist temple. They have a tradition of centuries of experience and offer good tips and technique, void of religious dogma.
At one time, I wanted to get into Kriya Yoga, which is just meditative yoga, but several things turned me off, mainly cost, secrecy and some thinly veiled cult like ritual that would not fly in other situations. And I have met no seemingly honest graduates of any such class or group.
Philippians 4:8 Finally, brethren, whatever is true, whatever is honorable, whatever is right, whatever is pure, whatever is [a]lovely, whatever is of good repute, if there is any excellence and if anything worthy of praise, dwell on these things.
What came to mind is a most excellent book by Dr David Burns called FEELING GOOD: The New Mood Therapy. While Cognitive therapy has been around for decades, and many practitioners use self-hypnosis, a form of meditation to augment it, Burns sets out the basics in easy to understand, laymen's terms. While Philippians 4:8 tells us what it is, Burns tells us the HOW to get to that point. And his basic premise is HOW to dwell on those good things, which sadly, many people have trouble actually doing !
There was a good book
Your Thoughts Can Change Your Life: The Twelve Essential Attitudes for Health, Harmony and Happiness
It was written by Unity Minister Donald Curtis and I had an autographed copy floating around at some point. It is hard to find and not cheap, but it focuses again on the idea of dwelling on that which is good, which comes from God, the "Spiritual gifts" which cast away anxiety and despair and all the negatives that go with them
So In regards to meditation, yes, it works fro many people to erase the anxiety, fear and allow focusing on that which is Peaceful and Loving. Hope that adds something good to your already insightful post.