कि आती है उर्दू ज़बां आते आते

नहीं खेल ऐ 'दाग़' यारों से  कह दो 

कि आती है उर्दू ज़बां आते आते 

nahee.n khel ai  'daaG' yaaro.n se kah do

ki aatii hai urduu zabaa.n aate aate

It's not child's play, let it be known to all who yearn

That the Urdu language takes a long time to learn

DaaG Dehalvii 

दाग़ देहलवी 

I can vouch for the veracity of this couplet by DaaG. I have been trying to learn it for close to two decades. I know I am better than when I started. But I am a long way away from where I want to be. 

There is another beautiful and oft-repeated couplet in this Gazal. You can read it here