"And be ye kind one to another, tenderhearted, forgiving one another, even as God for Christ’s sake hath forgiven you."
"Now the Spirit speaketh expressly, that in the latter times some shall depart from the faith, giving heed to seducing spirits, and doctrines of devils; Speaking lies in hypocrisy; having their conscience seared with a hot iron;"
1 Timothy 4:1-2
Having a tender heart is equivalent to having a tender conscience, and tenderness of conscience is vital in our relationship with God. It is dangerous to become hard-hearted and to develop a seared conscience so that we can't really tell if we are doing anything wrong or not. The key is to learn to quickly repent whenever Heavenly Father convicts us of something, not make excuses.
When Heavenly Father shows you that you have done something wrong, just say: "You're right, I'm wrong. I have no excuse, so please forgive me and help me not to do it again."
It is amazing how much that will help us have a tender conscience toward our Father in Heaven and a positive mind. But as soon as we try to reason things out and make excuses for our wrongs, we start getting a little callou on our conscience. It becomes just a little bit harder for us to feel than the time before.