The sad thing about writing fanfiction

Writing fanfics has given me this feeling I've never felt in a long time.
I'm suddenly transported to my earlier years, the period where I sincerely believed that I could plan something and make it happen.

Yet I'm guilty because another voice inside me tells me, "Why are you wasting your time and sweat to create stories based on another company-owned people? You could actually create your own original, sell it online, and make profit!"

Whatever satisfaction I feel vanishes, and I fall back into a slump.

I wonder how many fan fiction writers, or writers even, feel the same way as I'm feeling right now?