There will be always a reason for that pain

I quite like this moral of story brought by below message.
No Pain No Gain… Accept the Pain, Future will be Fruitful…
Don't feel the work you are doing is pain, because there will be always a reason for that pain or work.

Don't ever complain your senior gives you too much of works. Maybe he wants to put some money into you pocket. You must appreciate whatever he gives and teaches.