One Goal?

I feel like so many aspects of life affect each other. With that said, I can’t completely understand the focus on one goal at a time.

I do know I’ve struggled with being an all or nothing personality (loved the recent podcast). And I have been known to over-task myself.

But, even with those issues, I feel like when I concentrate on EVERY area of my life, everything is better. And when one area suffers, all areas are affected negatively.

So why should losing weight be the only goal instead of losing weight (which includes micro-goals of eating right, exercising, hydrating, proper sleep) AND working on a college degree AND growing spiritually be simultaneous?

This is just an example that incorporates 3 different areas.
Thanks for any input!