An E. concept comparable to the G. Atem in this idiom? Nothing explicit, as far as I know. I guess one could argue that the idea can be at least implicit in the concept of “staying power,” which works for “langer Atem” in certain contexts.

THX

I took stamina & motivation

to be in it/sth. for the long haul

https://idioms.thefreedictionary.com/for+the+...

for the long haul

For a long period of time; permanently or for as long as something takes to accomplish, attain, etc. Usually refers to one's commitment to someone or something.

If you need something bildhaft the suggestion above might work. It wouldn't work in the sentence in the OP, however. You would have to adapt it to the context, but it seems like a similar concept.