Fishing by working a lure or bait will make your body sore! I've fished professionally for many years casting hundreds of time a day. Like any athlete, you have to build up to it with proper technique. This is not a bad post.

Cast and then retrieve while your rod support hand is in the sweet balanced spot on the rod.

Check the rod for this spot with the lure tied on. Lay the rod horizontal on your index finger. It will teeter high or low on the sides. Move the rod back and forth side to side until it balances horizontal.
This is your sweet spot.

For bottom water fishing, balance the rod so the tip end starts to tilt vertically high. It has done a lot of the leveraging for you.

The same technique for top water fishing where you want the tip pointed down so you can walk the dog. Balance the rod tip to point downward. Let the rod do part of the work for you.

The more times you cast, the more chances you have at catching more fish or cover more territory.

Keep a shoulder rub with you and take aspirin or ibuprofen to reduce the inflammation where you hurt.

If you just want to cast a bait and let it sit, then it really doesn't matter.

This was not a bad post.
Many fishermen will not push that hard to improve themselves.

An old saying: 20% of fishermen catch 80% of the fish.

Don't give up. Turn around and do it all over the next day.