From the CBO-a paragraph or 2. It's PDF and a whole lot of info if you want to read

...eliminating or reducing the fiscal restraint scheduled to occur next year without imposing comparable restraint in future years would reduce output and income in the longer run relative to what would occur if the scheduled fiscal restraint remained in place. If all current policies were extended for a prolonged period, federal debt held by the public—currently about 70 percent of GDP, its highest mark since 1950—would continue to rise much faster than GDP. Such a path for federal debt could not be sustained indefinitely, and policy changes would be required at some point.

The more that debt increased before policies were changed, the greater would be the negative consequences. Large budget deficits would reduce national saving, thereby curtailing investment in productive capital and diminishing future output and income. Interest payments on the debt would consume a growing share of the federal budget, eventually requiring either higher taxes or a reduction in government benefits and services. In addition, rising debt would increasingly restrict policymakers’ ability to use tax and spending policies to respond to unexpected challenges, such as economic downturns or international crises. Growing debt also would increase the likelihood of a sudden fiscal crisis, during which investors would lose confidence in the government’s ability to manage its budget and the government would lose its ability to borrow at affordable rates. Moreover, the longer the necessary adjustments in policies were delayed, the more uncertain individuals and businesses would be about future government policies, and the more drastic the ultimate changes in policy would need to be.

www.cbo.gov/sites/default/files/cbofiles/.../FiscalRestraint_0.pdf