It can turn out to be selfish if you prioritize your self care over the care of your significant others. I think we all deserve a bit of self care, and I think it's okay to take time for yourself. But I think your significant other also needs to be able to take their own self care if they want it.
I think we all deserve self care, but it shouldn't affect ones relationship and one should not focus on just their self care over their relationship. Because when it does, it starts to cause a rift in a relationship.