Use daily positive thinking and change the outcome of your day, you will find lots of opportunities through your day to throw out the negative thoughts.
Be aware of when negative thoughts come to you, and rather than running with that thought, choose to focus on a thought that makes you feel good.
If you often get thoughts about the past that bring you down, then as soon as they pop into your head, think of something that makes you happy in the present and focus on that.
If technology breaks or freezes and you cant use it for a while, instead of getting angry and frustrated, think about the positive - you can now take a break and relax; the problem will get sorted, at some point. I learnt this the hard way after having to buy a new laptop, because heavily banging it to get it to go faster did not work.
Traffic can be the absolute worst! If the traffic is heavy the usual thought you may have is "It's going to take me ages to park", or something like that. Turn that thought around and think about it being fate, and that it is possible for you to find a parking spot easily and quickly. Everything comes at the right time - let it come to you easily.
Getting over my road rage is the best thing for me that's come out of positive thinking. Angrily driving around and dwelling on how other people use the road can absolutely ruin your day, it's starts your day off negatively and then it seems that everything keeps going wrong. Use your driving time as you time! Try an audio book or listen to your favourite music, bat off angry and negative thoughts about other drivers.
Don't get dragged into other peoples negative thinking, a co-worker may complain about various things and before you know it you're there complaining along. Instead, talk about some positives of the day, complaining leads to lower moods, lift up your mood instead of dragging it down.
Wake up and tell yourself that you are happy, feeling great and that you are going to have an amazing day today! (This doesn't have to be out-loud).
If you've never tried this before then you might think it sounds a little daft and that nothing will change for you. This absolutely works for me though, there are always days when things irritate you and get you down but my best days are when I'm knocking those thoughts away and making myself look at the positive side of situations.