Optimism is indeed an attitude.  It is the glass half full.  It is the reward for accomplishment.  And achieving it can be done.  How bad do you want it ?  It requires hard work and discipline to turn around a bad attitude, but over time it can be done.

First off, establish goals; write lists of things that need to be done, regardless of how small or insignificant.  When making lists of goals for the purpose of changing attitude, make the goals short term and very attainable at first.  Get yourself a stenographers notebook so you can flip back and forth and see what you have done or left undone.  Date the pages for easy reference and to establish a chronology.  A to do list will show you how much you have actually done during a day, and you might be surprised at just how much you do get done and it will also help to organize yourself and your approaches.

Once you get down a daily list of things to do, branch out and begin to establish goals that require one or two weeks to accomplish, perhaps in a separate book to keep things less confusing.  Then branch out to month long goals and after maybe a year or so, dare to begin of thinking about taking on longer term goals such as home improvement, getting a new car, going back to school, whatever, but begin to reward yourself with longer term, yet highly attainable goals.  The sense of accomplishment is most gratifying and uplifting as well.

Also to be done concurrently, is to pledge to yourself, not to utter negative thoughts out loud.  Thinking them is one thing, but saying them out loud gives them power.  Deny negative thoughts the power.  This is a fundamental part of changing one's attitude.  Find the half full thing to say out loud.  There are at least two sides to everything, find the upbeat side to say out loud.  It will be hard at first, but over time, it will come naturally because your mind becomes conditioned to thinking this way, because you have consciously spent a great deal of effort finding the right words to express an observation.

A very important aspect of keeping the glass half full is to see the good thing you want.  See that goal accomplished.  Dare to say that the light at the end of the tunnel is not an oncoming thing.  Many people fear success.  They sometimes feel that things have been going well for too long and that they are over due for a calamity.  Don't go there.  This is part of the power of self fulfilling prophecy.  If you do not envision the worst, that outcome is less likely because you have not provided your subconscious with a long term task.  See the best possible outcome.  See yourself standing at the beach or at the top of the mountain or front and center on that stage, soaking in the wonder of accomplishment and pondering what to do next.  It is a most delicious moment and a reward unto itself.

This is an oversimplification of a process that is life long and takes up to several years of hard work and discipline to establish.  But on the other hand a bad attitude is learned over a long period of time as well.  If you approach life in this fashion, you will be able to look back over a period of years and see how the change took place.

Learn the difference between can I, may I and will I.  This distinction is lost on many people.  The will I is most powerful and transforming it to I will is the ultimate expression of confidence and optimism.

Lastly, it cannot be forgotten that depression ( a huge and important component in many cases of poor outlook and attitude ) can be chemical in nature and may actually require anti depressants to pull yourself out of a funk.  I was at one point, so far gone, that no one, not even family could be nice to me without trying to see an ulterior motive in trying to get something out of me.  I viewed every nice thing and good deed as patronizing.  It required chemicals to make me take a breath and count to 10 and reconsider what was actually happening in social interactions.  I had to learn to accept compliments and simply say thank you to them.  Over time, I found that people just simply wanted to be nice, not try and get something out of me.  It was a big step in learning how to relax.

You can try and accomplish all I have written above, but if your wiring is short circuited, them you will most likely end up only spinning your wheels.  There is no stigma in admitting that depression is real and has a hold on one's life.  Always, the first step to solving a problem is to admit its existence.  Needing drugs to accomplish the end of depression is not weakness, it is sometimes simply necessary.

This is the short version of a personal philosophy I established back in the 80's for the purpose of helping my employees get a grip on their lives and become a more responsible human being.  In 1993, I had to apply it to myself during one hellacious divorce.  I had to practice what I preached.  Even though I knew the answers and what had to be done, there was so much adrenaline and anger, that it required anti depressants as well as the right answers to hit the reset button.

Then in 2001, the love of my life re entered my life and I found an affirmation of my ideas by comparing notes with someone working the steps.  So many things in common with the program.  And then came the cancer and this is how I maintained my attitude and positive outlook to help me get through it.  A lesson learned with the cancer and almost all survivors, care givers, doctors and nurses will agree, you can have the best treatments available, but without the right attitude, the outcome will be in question.  If the right attitude can help you beat cancer, imagine what it can do for your life.  The right attitude can get you through anything.  This is the reason for trying to establish optimism as soon as possible.  It's the whole future.

Other components are changing the people in your life.  Leaving behind the woe is me's and the one's constantly blaming others for their own failures.  If it means leaving old friends and family behind, then so be it.  These people are full of negative energy and will suck the living will right out of you.  Meet new people and try to find ways to present the new you to these new people who know nothing of your past and your behaviours.  One is who they surround themselves with.  Hook up with winners and give the losers the heave ho.

Ya, I know talk is cheap, but words do have power.  Everyday I try and walk the talk.  It ain't easy, but once it is your basic nature it sure is easier.  Probably could go on much more, but this is enough for starters.

   Y'all

Addendum,

Try to find a way to perform a daily random act of kindness.  This is self-explanatory.