But I don't need one, and looking at like through those lenses, as you put it, always strikes me as silly. I merely exist, and use that existence to do things I feel are right, good or necessary until the day that existence ends. I think what I've chosen to do with my existence is rewarding, but that doesn't lend it any special meaning or purpose.
Then you do have a purpose,
Goji. You say you don't need one, but you also feel you have to "do things [you] feel is right," no matter what form that may take. That in and of itself is purpose, for it is not only what we decide to do in life that lends meaning and purpose to our existence, but also how we live our lives, depending on our "life perspectives." You may not realize it now, but in time you will come to understand.