Sounds to me like you are an ideal co-worker, although I also agree, that you need your own space, whether at lunch as you take your walk, or wherever you find a moment during your busy day, to re-focus on yourself and re-juvenate. It is not selfish to put yourself first, especially when you want to succeed at something special just for you or have a personal goal in mind. And, as best you can, if negativity comes toward you, try to be silent, smile, and in one ear and out the other!! Maybe this is wishful thinking, but what the heck, whatever floats your boat!!
My very best good wishes to you!
Joan