Make hay while the sun shines
When there is an opportunity, take advantage of it before it is too late. The chance might not last long.
وقتی فرصتی برایت پیش می آید، قبل از آن که دیر شود از آن استفاده کن. شاید آن فرصت زیاد در دسترس باقی نماند.
There are not many jobs in this small city, but in summer lots of tourists come here, so make hay while the sun shines. Find a job as a tour guide and earn good money.