Why is it a constant battle?

I've worked hard all my life to be a better person. Now when I was younger I wasn't working really hard to be enlightened or spiritual or less angry. I was working on being a good moral person with priorities in order, kids first, everything else after.

In the last decade I have worked on losing my anger and in the last five years I have worked really hard on becoming a more positive person. I have made major changes in both these areas and I am extremely proud of myself. I have also become more spiritual and by being more spiritual I am more in touch with my true authentic self.

I go long periods where there is nothing, no matter how big or small it is that can depress me or make me think that the glass is half empty. Then BOOM out of nowhere the slightest thing sends me reeling trying to find my center, my peace, my calm. My question is this...." Does it ever go away or are we always being tested? And if we are, does this mean I am failing or does it mean that I see things more clearly and still need to learn how to find my center?"

If anyone knows, please help. I will be open and interested in all ideas.

PS. I can still be thankful for my life and still be grateful I have healthy kids, and a wonderful husband and a terrific mom and a mother-in-law that I actually like, but sometimes I have to really kick it in to my head that my life is not bad, it's just a roller coaster ride.