“Now though sinful desires exert their power on the hearts of men, before the word of the Lord springs up into the blade, yet, at first, their influence is not perceived, and it is only when the corn has grown up, and given promise of fruit, that they gradually make their appearance. Each of us ought to endeavor to tear the thorns out of his heart, if we do not choose that the word of 
God should be choked; for there is not one of us whose heart is not filled with a vast quantity, and, as I may say, a thick forest, of thorns.” – From Calvin’s Commentary on the Parable of the Sower
Thorns hurt. But not doing the heard work of clearing them out is even more harmful.
CWoznicki Think Out Loud 