Probably the best example of this is the two evildoers crucified with Jesus. Each had done things which warranted crucifixion. Jesus was perfect – He was “numbered with the transgressors” (Isa. 53:12) because He was perfect, yet He took on the sins of everyone who would ever live. The other men were awful.
And yet, one of them, even at the very end of his life, realized who Jesus was. He knew Jesus was perfect, and that he wasn’t. So, he asked Jesus to forgive and save him. The oher one didn’t. This “thief on the cross” received mercy. Yes, there were times when people lost their lives because of someone’s misdeed, just like in football, if one player commits a penalty in football, the entire team goes back several yards and, in extreme cases, loses a down. God judged the heart of each person, though, just as He does today. If one of the people who died because of someone’s sin trusted in the Lord for forgiveness, then they still went to Heaven. It was just as true in the Old Testament as today – salvation has always been by faith.
What does this have to do with your rules? You need to seek God’s wisdom to gauge just how tough to be; and that will be different with each personality – remember the “love languages” book I recommended. A repentant heart can be treated more leniently than one that isn’t, or one that just fakes it; and sometimes only the Spirit can tell which is which. If there are extenuating circumstances to something – including possibly an earlier rule that you didn’t realize would conflict - you may need to take them into consideration. There are many different things to consider.
The bottom line is, never be a Pharasee. The Pharasees demanded strict adherence to rules without paying attention to the heart of a person.