Hoping my diagnostics heal, not hurt

One thing that I've been semi-wrestling with over the past week has been how to approach people.
That's vague: my main job, in the real world, is to see a person whole, make a diagnosis as to what is hindering them from better health, and suggest therapeutic approaches to improve the situation. This is not necessarily exclusively in the domain of the physical either; certainly emotional, relational, and familial issues are also part and parcel of my job on a regular basis. My training teaches me to look objectively at the holistic situation, and make suggestions. Kind of like an advice columnist, but I get paid more.
However, what happens if you see this in a friend, not a patient? It is far easier for me to look at a patient, who, for all intents and purposes, I don't know and I don't love, and say quite objectively what I believe the fundamental problems to be in their lives. Not so easy when it is someone you know and someone you love. I have noticed some massively large obstacles that are hindering a friend from really and truly fulfilling their entire God-given potential, and it hurts me to see that. It bothers me greatly when giants of our age can so easily be felled by a stone to the forehead. However, some of those obstacles are building barriers from me being able to point this out in any way that would be constructive.
So how does one do this, without making them hate you afterwards? I haven't been able to figure this out. Is it worse to ignore the fact that your friend's fly is down, or for embarrassing them by telling them they need to fix their pants? Sigh. I'm hoping they read this (though I doubt they will) in order to perhaps start opening the communication channels...