Like your home, every so often your mind needs a good decluttering, too. By externalising your thoughts — whether that be through writing, meditation, you name it — you can take a mental inventory and create a clear picture of how you've been investing your time and energy. In addition, you'll be able to identify the things that bring you peace and joy, including what doesn't.
Once you've recognised the positive and negative sources, you can then start to act accordingly. Whether it's something — or someone — it will be much easier to "look on the bright side" once you've eliminated the negative elements holding you back.