Very famous study https://en.wikipedia.org/wiki/Stanford_marshmallow_experimen...

Delayed gratification is hard, believe me, had my Dad not literally screamed at me to sign up for the 401K when I was 24 and entering the workplace, too many years ago to admit... Well, I am glad I had a Dad that screamed at me.

It always seems like a bad time to invest. But, if past is prescient, it is always a good time to invest.