We will water the thorn for the sake of the rose.

This proverb means there is a price to pay for anything good. To get something as beautiful as a rose flower, we should be ready to accept and deal with the presence of thorns. When we water the rose flower for it to blossom, we inevitably water unwanted thorns as well. Similarly, when we set our minds to achieving a goal, we should approach our tasks with a mindset that is ready to deal with the inevitable obstacles that will come our way. It's another way of saying that nothing good comes easy.