know only too well

know only too well

To be very familiar with something, usually something bad or unpleasant. A noun or pronoun can be used between "know" and "only." Oh, I know sleep deprivation only too well, what with three toddlers at home. We know only too well how stressful moving can be.
See also: know, well
Farlex Dictionary of Idioms.

know something only too well

to know something very well; to know something from unpleasant experience. (Note the variation in the examples.) I know the problem only too well. I know only too well the kind of problem you must face.
See also: know, well
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

know only too well

see under only too.
See also: know, well
The American Heritage® Dictionary of Idioms by Christine Ammer.
See also:
  • know (something) in (one's) bones
  • know inside out
  • know somebody/something inside out
  • know someone or something inside out
  • know something/someone inside out
  • know (someone or something) inside out
  • I know
  • a closed book
  • closed book, a
  • have no idea