300 Foxes and a Donkey's Jawbone
The only restraint on us is the power of the Holy Spirit to convict our conscience that our actions have consequences. That's why we have guilt. We've all sinned and fallen short of the glory of God, that's why we need a savior.
Preparing our hearts doesn't involve special diets or exercise, it comes down to taking two simple steps: believing in Jesus Christ, and confessing our sins.
When we get saved we're indwelt by the Holy Spirit, and that cleanses us of whatever other spiritual problems we may have been facing. That's when we're ready to stand before the Lord because we're in Christ Jesus.
There's spirit, like Oxygen (O), and then there are Spirits, like the Holy Spirit (ΩO). There are also evil Spirits. Spirits are vaporous molecules or compounds which are inhaled, dissolve in the blood, then enter our heart.
And they of the circumcision which believed were astonished, as many as came with Peter, because that on the Gentiles also was poured out the gift of the Holy Ghost.