Hardest part is starting. When you grind past the first two weeks of aches and pains and start seeing results its very easy to want to workout.

I only work out when I have some lofty goal that requires it, eg summiting a ring of fire dormant volcano. Otherwise why work out?

You don't. You just grind until you turn it into a habit. Then you will feel withdraw when you don't.

Best you can do to make it easy to get there is use a passing bout of motivation to get through the habit forming phase and pick something you think is fun.

Just make it a habit

It’s harder for me mentally not to workout…

You just have to do it for that long it becomes normal.

By force

Look in the mirror? This is not intended to be ugly.