The best way to unite idealism and realism, on the one hand, with principles and practice, on the other hand, is to embrace a philosophy of "muddling through" (first known use 1864). Especially in matters of national concern and even more so in foreign policy, muddling through appears to be the best approach. Just review your own life to get the individual perspective.
Muddling through means to do the best you can with what you have at the moment. You do so without forgetting your ideals but embrace a realism which acknowledges that noble ideals are daily crushed by brutal facts. You hold steadily to your principles but compromise them for small gains when the available alternatives are worse. Or you take the least bad when all other options are badder.
Revising Lucy from Peanuts, this is my old and continuing philosophy.
For today think Libya, Egypt, Yemen, Israel, Syria, Pakistan, Palestine, Iran, and on and on. Or think about many choice you have to make in your own life where the only available l paths have major consequences you wish to avoid and you have to to muddle though somehow, someway.
And don't forget that sometimes life is really, really good.