Sometimes on the days I feel good I forget to write in my journal and I only remember it when I don’t feel good. What can I do about this ?

Create a rule for myself like every morning when I wake up I take my journal and start writing. You can write: tasks, something you want to improve, how would you like your day to be, gratitude, intentions etc. You don’t journal only for your emotions but to fill the gap between your current self and your desire self.