A difficult task is like 'walking through treacle'

A low paid job pays 'tuppence a lifetime'

My mother in law had some classics including:

You're a long time dead (when persuading herself to spend money/ have an extra drink/dance or do anything which other people might frown on)

Better late in this world than early in the next. (when tempted to rush across roads or drive too fast)

Or there's
As welcome as a fart in a sari

And plenty of others which I can't think of right now.

Catrin