Certainly the mere fact that you were chosen for this task is an exaltation to which no one else in this universe can ever aspire. Allah, nevertheless, addresses His beloved messenger kindly. He comforts and reassures him and explains to him how He has given him unceasing ease. With hardship comes ease. Indeed, with hardship comes ease.
Hardship never comes absolute, without some ease accompanying it.
Indeed, with hardship comes ease. The repetition suggests that the Prophet had endured serious hardship and suffered much affliction. This reminder recalls the various aspects of care and concern shown to the Prophet and then reassures him emphatically. A matter which afflicts Muhammad's soul so much must be very serious indeed. With hardship goes ease, so seek relief and solace.