If you say that you will do something come hell or high water, you are emphasizing that you are determined to do it, in spite of the difficulties involved.
[emphasis]
I've always managed to get into work come hell or high water.
See full dictionary entry for hell
come hell or high water
said to mean that someone is determined to do something, in spite of the difficultiesinvolved
The chairman of the Senate Judiciary Committee says the all-male panel will havetwo female members this year, come hell or high water.