Parents reprimand, remind, and prod, "Say Thank you." Learning to be thankful is an important life skill. The inclination to take people and things for granted appears to be human nature.
There's a wonderful little book about one method for developing the practice, 365 Thank Yous: The Year a Simple Act of Daily Gratitude Saved My Life.The author, John Kralik, has a writing style that's enjoyable to read.
Life is hard, and for many, that's an understatement. When dark days come, the last thing we gravitate toward naturally is being thankful.
I've heard it said, "If it doesn't make you bitter, it will make you better." Even though it's true, it's not helpful to push away or deny the negative stuff. If you're sitting in the middle of crap, see it for what it is. When you're ready to get out of it, look for what you can learn from it.
What can this situation teach me: about myself, about others, and about life? When I look back at this time of my life, how will I be able to see that it shaped who I've become?
With the perspective of 20:20 hindsight, my most challenging times have helped me most. As an example, when I've felt personally attacked, it's allowed me to recognize how active my fear of disappointing others has been triggered. I hate these seasons. They really suck.
At the same time, I gain new roots of self-esteem each time I encounter the pattern. I learn to appreciate the strengths while lessening the need to be affirmed by others.
By the way, I don't send a Thank You note to those who triggered it in me; I'm not a martyr! Doing my best to wish them well in my heart and mind is not easy, but it is helpful.