Always do the hard part first. If the hard part is impossible,

Always do the hard part first. If the hard part is impossible, why
waste time on the easy part? Once the hard part is done, you're home free.

Always do the easy part first. What you think at first is the
easy part often turns out to be the hard part. Once the easy
part is done, you can concentrate all your efforts on the hard part.
-- "Programming Pearls", Communications of the ACM, Sep. 1985