The phrase "bitter experience" refers to a unpleasant or painful event that someone goes through, which leaves a negative impact or feeling on them. Full definition
Following bitter experience with recurrent fires and the occasional hurricanes (only two bad ones in thirty years) the people have been turning more and more to reinforced concrete structures. (ambergrisCaye.com)
Through bitter experience, I have learned that a mistake in position correlation is the root of some of the most serious problems in trading. (newtraderu.com)
We know from bitter experience how awkward it is to eat alone. (friendshiptravel.com)