It is hard to get enough practice with all the things going on in our lives. We need quality practice when we do get time. One of the biggest problems is people wait until right before hunting season and then try to cram what should be 12 months of practice into a couple of weeks. The results are usually disastrous.
Don't confuse conditioning your muscles with practice. Practice should be improving your form, not building your muscles so you can draw and hold your bow.
A lot of time people get tired after 12 arrows but keep shooting to try and condition their muscles. That usually destroys their form as well as causes target panic and snap shooting.
The best way to condition your muscles is to keep your bow out where you can draw it every time you walk by it. Pick it up, draw, and hold it as many times as you can. Do that several times a day.
That will build your muscles so you can practice your form when you shoot. It doesn't take a lot of quality practice time if your muscles are conditioned. Just shooting 12 quality shots a day will really help. That doesn't take much time so you will find you will do it more often.
Practice is not just trying to hit the bulls-eye. It is practicing form. It is a lot easier to hit the bulls-eye if you have good form. You should practice form as much as aiming. One of the best ways to practice form is shooting with your eyes closed. Aiming takes a lot of concentration. Your form should actually be more subconscious. The only way to make your form subconscious is to practice it without aiming. Get real close to your target so you won't miss and shoot with your eyes closed. Concentrate only on your form. Think about your back tension, squeezing the release, and follow through. You should start every practice session this way. Shoot 6 arrows with your eyes closed before you move back and start aiming. This will not only improve your form so you shoot better, but also helps reduce target panic and snap shooting.
Stay relaxed while aiming. That is easier to do if your muscles are conditioned. Let the sight pin naturally float to the bulls-eye. Nobody can hold the pin right in the center of the bulls-eye. It is going to move.
Just stay relaxed and let it float while squeezing the release. You will find the arrow usually hits the bulls-eye. Nobody knows why that works, it just does. You will usually miss if you try to force the pin to the bulls-eye. We refer to this as a "drive by shooting". Tension in the body usually makes the sight pin move more so we tend to force it to the bulls-eye.
The most common causes of tension are poorly conditioned muscles and too long of draw length. You can't relax if your draw length is too long because your muscles are extended. Most archery coaches say 80-90% of the bowhunters have too long of draw length. Some use too long of draw to try and get more speed. Others may add a string loop, which shortens the draw by up to ½". Try shortening your draw if your muscles are conditioned and you have trouble with tension. That will usually reduce other problems like target panic.
Remember that your equipment is closer to perfection than you are. It is more likely you rather than the equipment when something changes. You should have all of your equipment settings marked or recorded. Check your marks or records if you are shooting off one day. It is probably you if nothing has changed. Don't start making changes to your equipment unless you can see it has changed. Try shooting up close with your eyes closed to concentrate on your form. Don't change your sights or equipment unless you find that you hit the same place over several practice sessions.
Don't shoot if you are frustrated, pressed for time, or don't have a positive attitude. That will only cause more problems. You are better off with no practice that day than bad practice.
Always end your practice session before you are tired and your groups suffer. You want to end with a positive attitude. That will make you shoot better next time. You want to remember those arrows in a tight group, not spread all over. Shooting good is a matter of confidence. You lose confidence when you end a session with poor groups.
Practice for hunting season with the clothes and equipment you hunt with. Adding gloves, bow quiver, face mask, or bulky clothing will change the way you grip your bow, bow balance, and your form.
The most important thing is quality practice. Twelve quality shots a day is much better that 12 quality shots and 24 bad shots. It doesn't make much sense to practice bad habits.