The default position of every human heart (my heart and yours too) is legalism and self justification. The words below are from an article at The Resurgence entitled
I Just Need To Give Myself Grace:
We all create rules to follow that make us feel like we’re closer to God. This is a sin called legalism. We add rules that God doesn’t ask us to follow, feel good when we do them, or bad when we don’t, and in the process we create a new law.
Your laws are a burden
Some people make daily Bible reading into law. They feel
justified and holy when they read, but guilty when they don’t. This is
messed up because the point of reading the Bible is to draw closer to
God, to love him more, understand him better, and have your heart
transformed—but it’s easy to take the gift of the Bible and turn it into
a burden. It only becomes a burden when you use reading the Bible or
any other new law that you create to make you feel righteous, instead of
understanding that you are only made righteous by Christ.
You can't do God's job
You can often tell someone has created a new law for themselves when they use a phrase like, “I need to give myself grace.”
When you catch yourself saying this in your heart or aloud you need to realize that you’re assuming two things:
1. You’ve created a law you’re not following.
2. You are assuming God’s position in trying to give yourself grace.
It’s so easy to use Christian-sounding words in
anti-Christ ways. Repentance is a good thing; it’s one of the great
gifts the Father gives us, the Son won for us, and the Spirit empowers
us to do—but the important question is “who are you repenting to?”
Don’t repent to false gods, ever
When you create your own law and violate it, you are
sinning against the false god of self. When you worship money and don’t
have enough, don’t repent to it and pour yourself out for the money.
When you worship sex and don’t have it the way you want it, don’t repent
to this idol and bow down at other altars. When you worship ministry,
don’t offer your spouse, kids, and relationship with Jesus on this
idol's altar. Repentance to false gods will harden your heart from true
repentance....
More at the link above.