The promise is not that the Lord will remove the load we cast upon Him, nor that He will carry it for us but that He will sustain us so that we may carry it.
He does not free us from the duty but He strengthens us for it. He does not deliver us from the conflict but He enables us to overcome.
He does not withhold or withdraw the trial from us but He helps us in trial to be submissive and victorious, and makes it a blessing to us.
He does not mitigate the hardness or severity of our circumstances, taking away the difficult elements, removing the thorns, making life easy for us but He puts Divine grace into our hearts, so that we can live sweetly in all the hard, adverse circumstances.
2Co 12:9 And he said unto me, My grace is sufficient for thee: for my strength is made perfect in weakness. Most gladly therefore will I rather glory in my infirmities, that the power of Christ may rest upon me.
Php 4:13 I can do all things through Christ which strengtheneth me.
~J. R. Miller~