If you're feeling depressed and finding it hard to be happy lately, it might be worth going to see your GP. You don't have to suffer in silence with this - depression is common, but not an unimportant condition.
Something that I have found really helpful for my mood is mindfulness - it's all about being aware of your thoughts, feelings and emotions. Some call it 'falling awake'. I've found an app called 'Stop, Breathe & Think', and it guides you through meditations which you can choose according to your mood. They have a website, where you can download the app for Android or iOS and you can use it on the web.
Hope this helps, and good luck.