આજ કાલકે કરતેહી, અવસર જસી ચાલ;

āja kālakē karatēhī, avasara jasī cāla;

Literally: By doing 'today' and 'tomorrow', the opportunity will slip away;
What it means: Warns against procrastination, as delaying tasks causes valuable opportunities to be lost forever.

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.