know (all) too well

know (all) too well

To be very familiar with something, usually something difficult, bad, or unpleasant. A noun or pronoun can be used between "know" and "(all) too well." Trust me, I've got three kids under six, so I know too well how debilitating sleep deprivation can be. A: "Do you have any idea how stressful the application process is?" B: "I know it all too well. I went through it myself several years ago."
See also: know, well