I think sometimes, when a relationship is going badly or has ended, it can be easy to convince ourselves that the partner who is getting on our nerves was lying all along, rather than that they have changed/grown or that we misunderstood them (maybe because we heard what we wanted to hear, rather than what they were actually saying). Doing this comfortably assigns blame away from ourselves and onto a person we are already angry with or resentful towards, and means we do not need to feel responsible for our part in the relationship ending. It's not helpful to do this, though, either in terms of self-development or in terms of rebuilding that relationship as a friendship in the future.
Personally, I think blaming is never helpful anyway, either self-blame or blame of others. Sometimes we assign blame because otherwise we would feel the need to blame ourselves. The solution is to be compassionate and understanding of *ourselves* as well as of others. We are not perfect, and we can't be: we can only do our best at the time, and be totally honest about who we are and what we truly believe we want *now*, while recognising that that may change in future.
Another part of the problem is the weight our culture places on the longevity of a relationship, and the sense that the end of a relationship is a failure. So when a relationship ends, there can be a scramble to paint ourselves as the wronged party, and to assign blame to our ex-partner/s ('S/He lied!') so that friends and family will sympathise with us rather than blame us. But to paint oneself as a victim is never helpful, as it is a position of weakness that can be hard to see our way out of. Taking responsibility for those things that are/were our responsibility is a much stronger position, because then we can see a way forward to changing those things that are not working. Sometimes, perhaps often, there is objectively nobody to blame for a relationship not turning out the way we hoped, and no deliberate wrong-doing, perhaps only some self-deception. Sometimes, people are simply not as compatible as they thought they were, and they are better off apart than together. Understanding this, and learning what we can from that relationship - even trying to be grateful for the lessons we have learned - can be a growth experience in itself, although it is, of course, painful to let go of the hopes and dreams we invested in that relationship.
On the other hand, if it is clear beyond a shadow of doubt that we have been deliberately lied to, we have reason for anger, but also reason to end any commitment based on that lie without compunction and without beating ourselves up emotionally for the pain ending it will cause the lying partner. A clean break, and move on. We can be compassionate of them and the reasons they had for lying without allowing ourselves to continue to be a victim of their lies.