Newbie here. "Endure suffering" - but how do we know if we're suffering due to our own choices?

I am a newbie so please forgive me if I have this wrong.

As I understand it, followers of Christ are called to endure their suffering instead of avoiding it. There lies the real "work" of Christianity in order to heal the soul.

However, I am wondering - what if the suffering we experience is due to a non-spiritual factor?

For example, I have been a long-time strict plant-based eater. Only recently did I discover that a lot of my mental anguish was not actually due to the circumstances I thought, but rather because I was severely malnourished. A test showed I am severely deficient in many minerals and vitamins, affecting testosterone and other biomarkers. For the longest time I had no idea that many of my low moods were directly caused by a lack of quality fats and proteins. But before I realized this, I thought somehow that my spirit was being punished or tested (albeit within kind of a new-age approach).

I have read a few stories of saints performing extreme fasting/ascetic practices where they eat scant diets for penance. They suffer in the name of Christ, as far as I'm aware. If they became malnourished and physically feeble, although their faith is strong, how exactly is this suffering due to some higher spiritual struggle rather than self-imposed? And how do we know the difference?

Another example I can think of: Many of us in the modern world are isolated and for various reasons, have few friends or confidants. Humans without a true support system inevitably suffer because we're not meant to be islands unto ourselves. Couldn't a Christian mistake the effects of lack of intimate human contact, with a test from God? The pain felt from isolation obviously can be remedied by some contact, and yet, how would we know if we attributed that pain to a higher purpose?

The overall question is:
How do we determine what is a genuine call to endure suffering from God vs. a call to rearrange our life in order to practically lift us out of suffering?

There are obviously easy targets: If we are addicted to drugs or alcohol, or if we're avoiding positive life decisions that we KNOW we can make, then of course we will suffer. I am talking about changes that we don't actually realize need to be made, and still hurt us, resulting in a miscalculation that we are somehow meant to willingly endure the struggle.