Tim Bowen shows he's at the peak of his powers with another fine article on idioms.
'After their 3-0 defeat in the first leg, they will have a mountain to climb in the second'. If you have a mountain to climb, you have a very hard, if not impossible, task to fulfil. If you have a mountain of work to do, this also suggests an arduous task, as in ‘He was buried under a mountain of paperwork’.
To move mountains means to do something so difficult that it seems almost impossible or to make strenuous efforts to achieve something difficult, as in ‘They called on the international community to move mountains to help the flood victims’. If you make a mountain out of a molehill, you treat a minor problem as if it were a really serious problem, as in 'Some people believe that the so-called swine flu epidemic was a fuss about nothing and that the authorities were making a mountain out of a molehill’.
If you are on the slippery slope, you are in a situation that is getting worse and will become extremely bad unless it is stopped, as in ‘There is a widespread belief that these policies will put us on the slippery slope to government control of the internet’.
To be over the hill means to be no longer young and therefore no longer able to do the things you could do in the past, as in ‘At 35, he is regarded by some people as over the hill but he is still capable of doing a good job for the team’. By contrast, if you are at the peak of your powers, you are at the time when you are your most successful, as in ‘Beethoven was 19 and at the peak of his powers when Napoleon’s army occupied Vienna’.