〜てからというもの

Meaning

Indicates that ever since a certain event, a state has continued the whole time afterward. States that a change took hold marked by some event.

Examples

子どもが生まれてからというもの、自分の時間がほとんどない。 Ever since the baby was born, I have had almost no time to myself.
あの失敗をしてからというもの、彼はすっかり慎重になった。 Ever since that failure, he has become completely cautious.