Misquotations pop up in the strangest places.
Today, I was at a stationery store (it was stationary, too, by the way) looking at anniversary cards. (Don’t tell my wife; I’d like to surprise her.)
There, I found two which each referred to the same Hermann Hesse quotation. However, the quotes did NOT MATCH.
The one on the top (at right) apparently captured the quote correctly, with the important IF at the beginning.
The other one (below, at right) snipped off the IF. The proper rendering (translated from Hesse’s novel Narziss und Goldmund) is:

If I know what love is, it is because of you. [Boldface added.]

Without the initial IF, problems arise. For one thing, this leaves two independent clauses with a dreaded “comma splice” between. But the real problem is bigger than that. Here’s an example of a lazy approach to quotations.
Oh, I almost forgot. There’s another problem. Both cards spelled his first name wrong, dropping the second -n. At least they were consistent!
Back to the quotation…..
I see from one Web site that Hesse’s quotation in German was:

Wenn ich trotzdem weiß, was Liebe ist, so ist es deinetwegen.

I ran it through Babylon and got this:

If I, what love is, nevertheless know, so it is as far as you are concerned.

Google handles the translation this way:

If I still know what love is, it is because of you.

Not bad! I like the “still”.
And the elusive “IF” is in both.