Ultimately, God is the source of all health (Ps 62:6, Berkeley note). Most of us want to be healthy. Many of us, however, don’t want to do the kind of things that contribute to health. Besides, health is relative. Even those who are healed are not necessarily healed as effectively as the man in Mt 12:22 (Barclay). Furthermore, health includes spiritual health, mental/emotional health, relational health (that is based on the behavior of others) as well as physical health. No one is fully healed in this life.
We have our part to play that contributes to how healthy we are. It is common knowledge to talk about proper sleep, exercise, food intake, and medical care. Yet, a number of biblical passages also mention some things we should do: be cheerful (Prov 17:22, TEV), confess our sins promptly (Jas 5:16, ISV), regularly pray for our own health as well as the well-being of others (Jas 4:2), and be in close fellowship with the Lord (Isa 53:5, CJB alt). Other things would be to relax and avoid unnecessary stress (Prov 14:30), deal appropriately with anger (Prov 14:30, Lamsa), and address demonic influence in our lives (Acts 10:38, Berkeley).
If we would do our best to be as healthy as possible, we cannot ignore many things we know are vital to being healthy. We normally reap what we sow (Gal 6:7). Let us, then, sow to what makes for health (Gal 6:8). In doing so, we can live out the full number of days the Lord has for us (Ps 139:16), with the full measure of health He wants, so we can most effectively do all He has called us to do.
Instead of being timid, learn to be appropriately bold.