Writing is not easy. It requires a vast amount of creative energy, focus, time, and willingness to learn. If you don't meet a personal goal, be it a word count or a sales number, forgive yourself and move forward. Perhaps you need to strategize, or perhaps you just need to rest. But lingering on the "failure" is not forward momentum.
My mother kept a journal for me beginning in pre-school, in which she documented my favorites, aspirations, awful 80's-baby permed hair, and terrible handwriting. Since I was 5, I indicated I wished to be a writer when I grew up.
I don't experience "Writer's Block" per se, but I do experience burnout.
I believe you must take good care of yourself to feed your creativity. If you're struggling, you may need to take a real break: reading, movies, games, hiking, just something that you enjoy and can rest your mind. Take care of your mental health. As I said earlier, also give yourself the grace to do this without guilt.
I have very rigid schedules to structure my writing time, so when I get back into it, I adhere to the schedule whether I "feel like writing" or not. I have numerous rituals when I start writing from which I do not deviate. I believe these processes help get my mind in the right place when I do decide I'm ready to write.
