Are the lies to avoid doing a specific task? Or to avoid a certain reaction from others?
I think the approach you take depends on how high-stakes the lies are and if they affect people other than the person who is lying. If the lies will have financial, emotional or health consequences for others, I don’t think that’s something anyone can or should tolerate. In that case, I would separate as much of that part of my life from the person who is lying.
My husband lies, and it’s generally to stay out of “trouble”. I’ve come to realize that it’s generally because he agreed to something he didn’t actually want to do. So he does what he actually wants to do and then lies to cover up his actions. It’s hurtful. Many times it’s about something minor. I guess knowing why he lies gives me some sympathy, but I haven’t found a way to get to compassion, to be honest. But I deal with it myself by putting up boundaries and checks where I know I can’t trust him. And I try to get actual agreement on things, so that he doesn’t feel he has to lie – first lying about agreeing to a plan, then lying to cover up that he didn’t follow through on the plan. It’s not ideal though, and if it’s your partner that’s lying, it’s very hard to feel like it’s an actual partnership. I’m sorry you’re in that situation.