You aren't trying to run all your runs at your goal pace are you? Most of your training runs should be a good bit slower.
Some days you cant find a groove. You just cant. But if it is happening more often than not, my guess is you are running way too fast most of the time. You are racing your training and wearing yourself down instead of building yourself up.
Ignore the pace. Go out and run without a watch ( or hide the watch if you MUST know later). Listen to your breath. Find the breath that gets you in the right rhythm regardless of what that pace is.
But just for reference (and if I knew your goal I could get more specific).
Your long run should be 1-2 minutes per mile slower than
your goal pace.
Most "normal" runs should be 1-1.5 minutes slower than your goal pace.
Only during tempo runs and interval work should you be faster than your goal pace and depending on how much running you do that should only be once MAYBE twice a week (if you run 5-6 days)
On the goal. I see nothing wrong with having a goal as long as the goal is realistic. There is a lot of time between now and October 17th. If you have not run a shorter race (5K or 10K) find one between now and then.
A
calculator like McMillan can give you an idea of an appropriate goal as well as appropriate training paces. Note that if you are a newer runner the HM prediction is likely to be faster than reasonable.
MTA: and generally no matter how crappy my training runs have been going, race days are good days more often than not. I have only once or twice had a race where I absolutely could not pull it together.
MTA2: And if it is hot where you are, take the runs even slower. Heat is a big drain on pace. The important part is appropriate EFFORT. If you are killing yourself in the heat trying to hit some arbitrary pace, then it is the wrong effort. The right effort will return you the faster times when the weather cools off.