To help solve this problem, I created a long-range planner for recording all my random ideas. There's a box for each category and month so I can write down thoughts whenever the inspiration hits. Then over the summer, I can use the planner to help me map out the following year's curriculum. You can also use this long range planner as a pacing guide to help you see your monthly themes and big ideas at a glance.
Download the form for free on my Purposeful Planning page. You can also find lesson plan pages for daily lesson plans and a language arts block planning form.