સુખ સજ્જનકે મિલનકા, દુર્જન મિલે જનાય;

sukha sajjanakē milanakā, durjana milē janāya;

Literally: The joy of meeting a good person is realized when one meets a wicked person.
What it means: The true value of virtuous company is only fully appreciated after experiencing the misery of dealing with bad people.

Also said as

ગુજરાતી કહેવતસંગ્રહ (Gujarati Kahevat Sangrah) (1923) · read from the scan by machine — the Gujarati itself is unchecked · English is machine-made and nobody has checked it yet

Heard it differently, or know we've got the sense wrong? Tell us — that is exactly the kind of correction this needs.