Here's the second verse of Rabbie Burns' poem, John Anderson My Jo...
John Anderson my jo, John,
We clamb the hill thegither,
And mony a canty day, John,
We've had wi ane anither;
Now we maun totter down, John,
But hand in hand we'll go,
And sleep thegither at the foot,
John Anderson, my jo.
A good example of life seen as an upward climb, followed by a slow, tottery downhill slope towards death. It's pretty clear that the downhill leg is - whilst still companionable - not nearly as 'exciting' as the uphill one was. A perfect illustration of the use of the phrase exactly as Crisgal presents it, despite the fact that it can be used to mean the virtual opposite!.