RE: Why do I struggle??
VA, I'm no expert but my "advise" (take it for what it's worth but this is from personal experience) is similar to everyone elses:
Check your equipment first of all and make sure it's all in specs, arrows are correct for your set-up, etc. Sometimes tiller adjustments can help.
If all that is cool, then make sure your anchor is consistent and that you have no torque issues. Also make sure you don't punch the target and make sure you follow thru (especially on the long shots).
Are you having problems holding steady? If so, maybe you need a heavier, out-front type stablizer.
If you think it's a good shot and everythingfelt right, does it still end up being way off? I know right off if I missed the mark, usually my pin wasn't settled at the release assuming release was smooth.
Lastly, if all other remedies are tried and don't work, maybe a more forgiving bow should be considered?
Just more food for thought, good luck and have fun.