My circumstances have changed in many quantifiable ways lending to my contentment but it's mostly because I started to see that I could actually effect change and somewhat control my destiny. When you feel helpless and stuck it's not a recipe for sunshine and fairy dust. Finding my own sense of worth and power helped immensely but it is also tempered and complimented by acceptance of the things I cannot control. There are still times I'm exhausted from a long day at work and could begin to complain but why? That tiredness is just a fact of life and I have accepted as part of life for now.
People say "I really wish xyz hadn't happened" or "wish you hadn't done..." That mindset puts an emphasis on the past instead of the present (which you have the power to mold). Instead we should say "I'm upset by xyz" and then deal with it. Wishing to change what has already happened shows a lack of confidence and / or drive. Actually, focusing only one (the past, present or future) is a recipe for mental illnesses like OCD. When you don't feel like you have the capacity to deal with life as it happens you try to preemptively set the stage which is a fairly futile endevour. Alternately ignoring the past and future and only living in the now is foolish because you can't learn from your mistakes or make wise choices when you don't consider tomorrow. Then there are those who live only for the future, the drive to make things perfect, but they miss out on the beauty of each day.
Happiness is about 40% environment and 60% perspective. If you live in a free part of the world you have control over your environment but perspective is something you can change anywhere. No matter what your station in life, there are going to be menial parts that are annoying - I mean everyone has to poop and pay taxes right?
My life is fantastic! I have a great job, amazing partner, beautiful healthy children and am pursuing my interests. Could some of those things go away? Yes but at least now I know that there are nearly limitless possibilities that I am capable of effecting. When you believe the world is your oyster, there's nothing to be upset about.