This is a very old saying, but it still applies to us today. There is no real reason for a teacher to have to write every single lesson plan from scratch. There are tons of resources available to you.
First of all, there is the Internet. Now, of course, anyone can put anything on the Internet, so you have to sift through a lot of junk to get to the good stuff, but a lot of it is free. Start with major websites of your local ministry of education. The Ontario government had a unit planning software created called OCUP (that I'm not the hugest fan of) and on their website they have complete unit plans for the new curriculum in pdf form based on their software, so that's a great place to start. You might not have to come up with anything that way. Look around, there are a lot of good teacher sites on the Internet.
Secondly, there are other teachers. Colleagues are a fantastic resource to you. Why not find another teacher in your board or school that teaches the same grade as you and swap lessons? They plan math for October, and you plan science... Or get a group together. You don't have to have long meetings, you could just email each other your lesson plans, if you want. Also, some retiring teachers and teachers that are changing grades and/or classes will be more than happy to give you their old lessons.
Now, I know that this can sound a little too cookie-cutter, where everyone is doing exactly the same thing, but once you get a lesson plan, there is no law that says you must implement it as is. Play with the ideas in it, tweak it for your teaching style, and have fun with it! Once the major part is done, you have the freedom to be creative.
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Have great day!