Forgiveness and trust?

I love my family, I really do. There are times I have to remind myself that I do, but really I do but when do you draw the line? I had mentioned before that I let them come and stay when they needed a place. I have given them food when they were hungry, and helped with money when we could afford it and at some times when we could not but they were in great need. But when they turn around and lie to you, or abuse your willingness to help to the point where it costs you emotionally, financially and such when do you draw the line? When they tell you something and you can feel with everything in you and your common sense says it's a lie do you confront them and have them lie to you more and turn into a big fight as they defend what they know is a lie and you know is a lie but they can't let themselves admit it because of pride and self preservation where do you draw the line? I understand that no one is perfect and I don't expect them to be, heck I am as far from perfect as a person can get sometimes and I love them no matter what, but when do you say enough is enough? When someone has continued to lie and cheat you and because it it your kids as well and they can't face that they have this problem when do you draw the line and say enough is enough? We are suppose to forgive 70 x 7 or more if needed, but how do you forgive someone while still having doubts if they mean their apologies or not help them again because you are pretty sure it will happen again? If you don't help doesn't that mean that you don't truly forgive them because you don't have that trust? This something I have struggled with my whole life to understand. And here I am in this same story again but different situation. And as you can see here I am finding myself pondering these questions again. The people concerned will be sorry, they will make attempts to make it better and mean it, they might even succeed in fixing this one like they have with others but what do I do? Ugh! It is at times like these that I wish I was the type of person to write other people off and never talk to them again. That would make this so much easier I think, lonely, but easier.