"Be satisfied with everything that life gives."
Translation:Var nöjd med allt vad livet ger.
The word "vad" is usually an interrogative pronoun. But in this sentence, "vad" is used as a relative pronoun instead of "som". (To use "som" would also be correct here.)
As far as I know, the word "vad" is used as a relative pronoun only after the indefinite pronoun "allt". Compare to German, where one says "alles was" instead of "alles dass".
In Swedish, to write "allt vad" instead of "allt som" sounds a bit more formal and bookish.