Find your joy.
Then, protect it.
Don't allow the negative emotions of others around you to dim the light of your joy. Feel sympathy, or even empathy for their plight, but if you get bogged down in their darkness, it's much harder to regain your joy, and even more difficult to help those who suffer.
Earlier, I found myself, in a semi-lucid, semi-dreaming state, considering this problem of getting bummed out when someone around me is down, and my desire to not be so affected. I found that in my mind's eye, I was watching my spirit wrap my joyful heart in a sort of wicker-looking casing, which was semi-permeable in that it allowed light to pass in and out, but would block negativity from entering. How wonderful! :)
This also comes on the heels of a recently revived, dissatisfied awareness of my occasional hip-shot negative reactions to other people's mistakes (mainly while driving...). I have a tendency to curse people who seem oblivious, and what I find would be my preference is to develop a new habit of just shouting blessings. To the person who is slowing down through a green light, presumably because they are unsure of whether to turn or proceed: instead of, "What the eff?! Can we make this light while it's green?! Go!!", I should like to respond, "Omni! Give this driver clarity!", or even just the quick version, "Clarity!" I want to spend more energy praying for people than criticizing them.
I believe that the more we shine our lights, the more light we will have in our lives. When others around us are not the joyful, clever beings we wish them to be, let's all just pray for them to be so, support them as best we can, and carry on with maintaining our own joy and growth.
Happy day! :)