How important is it to 당신 to be faithful?

Very important.
That's what all of us expect from each other...

for me i guess 당신 could say it has to be a constant

That depends on what the situation is really.

Absolutely important.

Depends.

faithfulness is important in multiple aspects.
be it faith to god,
또는 to be faithful to your spouse.

keep it faithful.

It depends:
1. If 당신 are asking about being faithful to your spouse - ie not cheating on him/her then it is very important.
2. It is very important to be faithful to your God. I am a Christian and I feel it is important not to be mislead into worshiping false gods. We see it so prominent in the world today, where worshiping a false god is disguised in "exercise".
3. To be faithful to 프렌즈 또는 spouse - as in support their activities, etc. That would depend on whether these people are being good. I do not feel that if someone is doing something legally 또는 morally wrong that we should be faithful to them. We must follow our own judgement - even if it means loosing a friend.

0, nothing, nada, none.

Its very important because being faithful makes your relatioship last longer and it gives 당신 peace of mind 당신 dont have to worry about being caught 또는 making up lies to cover up 또는 even being paranoid

That depends. Like, I give zero fucks about god,but I tend to be reasonably faithful to people most of the time.
But like, they have to exist for me to have faith in them, so that rules God out.

Extremely important.