How I can still get triggered

It seems for me that things can go along nice and easy, then boom.  Something will happen and take me back to doubt and fear.  HMMMMM wonder why????  Since I am one who will goes deep within to find my truth, this is something I want to figure out.  How can I have high self esteem for a long period of time and then start to doubt.  I found that my mother in law once again told my son a lie about me.  That sent me back to a place in my childhood.  Now sure when in my childhood,  but it sent me back.  I would think by now living with this woman for 4 years I would get used to her hurtful words.  But I will never get used to them.  They hurt my heart.  Since I never had the love of a mother, only abuse and manipulation from the 2 foster mothers I lived with, my mother in law seems to be not too different from those mothers I had to live with.  When my mother in law says those hurtful words like she did last Saturday, "What have you done for me Jeanette" I feel as tho I will never, ever be good enough for her.  I will never be able to show her love and caring and have it be appreciated.  She is meanspirited.  She has no compassion and if she did she hides it well.  Since I have lived there I have been a good daughter in law.  I have stood my ground when she is mean and used all the I statements regarding her verbal abuse.  I have never demeaned her, said hurtful words, just took care of my boundaries.  When she is nice, I am nice, when she is mean I retreat.  This is my way of keeping myself safe.  I must say it is getting old, very old.  I know I cannot change her.  She is 91 and is not about to go inside and look at how she treats others and also does not own her behavior and instead blames the family or "I am lonely, I am sick, I am tired of sitting here".  I do believe she is lonely.  She has choices to change that if she pleases.   But instead she plays the victim to the hilt with her son, my husband.   She has done this for the last 4 years we have lived here.   I truly am at a point in my life where i have nothing left to give.  I give of myself and my expectation is that that will be appreciated.  The little wounded child wants to be appreciated.  The adult in my knows that.  I am thrilled at the slightest inkling of any kind of caring from her.  Yes, I get the crumbs and am happy with the crumbs.  Intellectually I know I deserve respect and caring.  Deep inside I hurt because I am not getting that. I know even tho I stopped therapy that there is still much work to do on my psyche.  I know this journey is ongoing and even in this instance there is a lesson for me to learn.  Guess I want to know the lesson and pass it with flying colors. and learn something new.