But when you are teetering on a high wire, stability is difficult to maintain.
You don't stop building just because it is difficult to maintain the park.
Although this is difficult to maintain in any duopoly, it is not impossible.
It also is difficult to maintain and study appropriately some invertebrates under laboratory conditions.
But this balance is difficult to maintain, and lately there have been signs that America may be wavering.
Cork, which is not a synthetic, is handsome, but is difficult to maintain and is not exceptionally durable.
However, as the Italian philosopher Antonio Gramsci suggests, it is difficult to maintain the optimism of the will in the face of the pessimism of the intellect.
The board members added that it is difficult to maintain current investment as the rules of the game are constantly changing.
But it is difficult to maintain earnings growth while spending heavily to develop new products, so the company's stock can fall, leaving it vulnerable.
[The art world] is absolutely obsessed with youth, which is a shame because once you've had early acceptance it is difficult to maintain it.
During long passages the solo instruments have ruminative, intimate exchanges over a subtle orchestra backdrop, and it is difficult to maintain balances.
