the heart

I've read in the bible about God doing certain things to harden someones heart, so even when they see miracles they don't believe in God. Like the story of Moses and Pharoh in Exodus 7:3-4 "But I will harden Pharoah's heart and though I multiply my miraculous signs and wonders in Egypt he will not listen to you". Do you think there is anything a person can do if they realize their own heart is hard? Maybe they want to believe but can't. Maybe they want to have a soft heart. It seems all there is to do is pray like in Mark 9:24, "I do believe; help me overcome my unbelief". But maybe there is something else?