Long functions without reusable parts

You have a long function (like 100-300 lines) that describes a sequence of steps that only make sense together.

What do you do?

• Add some comments to show what the steps are, but keep it in the same function. No point introducing extra indirection and jumping around the code. If a part is ever reused, it can still be split at that time.
• Split it into multiple functions. Methods should stay short so as to give a faster overview. Who knows, maybe it'll be re-used one day in the future.

Bonus question: if the function is a method and you're splitting it, do you just share data through instance fields, or pass everything as arguments?

EDIT: I'm thinking about compiled languages with the possibility to force the compiler to inline these methods, so no performance cost. But performance considerations may be useful for other readers.