Utmost Duty to Oneself

Utmost duty to oneself is preservation of self. "Self" here refers to oneself - the person, all of that person → mind, body, etc. - all of it.

Negligence or being indifferent towards yourself causes serious damage and is the worst thing you can do to yourself.

What is preservation of self?

Nurturing, caring, being good to yourself, loving yourself all amounts to preservation of self. But there's more.

Positive thoughts, positive words, positive energy, being in a place with positive energy, being with people with positive energy are all required and accounts for preservation of self.

Equally, or even more important is keeping negativity away from you.

Negative thoughts, negative people, negative energy, people with negative energy, places with negative energy - be as far away from these as possible.

It is not worth giving these a try.

When a good apple and bad apple are kept together, the good apple goes bad, the bad apple does not improve. Such is life.

You have to be selfish even, in preservation of self.
It is your duty to be.
You are needed to be.
It is the morally correct thing to do.

If you aren't good to yourself, it's hard to be truly and fully be good to others. If you don't love yourself, it is hard to truly & fully love others.

Build a moat around you and protect it with might all the time.