Wow,no need to be discouraged. First year out and you not only saw a deer, but you were able to take a shot. That's a good thing! Heck, I haven't had a chance at a deer since the 3rd day of shotgun season last year!
Here's one wayI was taught to deal with flinching or jerking. Do a lot of shooting with a low power rifle (.22 cal or so)in the off season. This allows you to "train your brain" to pay attention to the shot placement and trigger pull without wearing out your shoulder. When the time comes to pull the trigger on that deer you're brain will be on autopilot and you'll be able to focus on the shot placement and trigger pull without the kick even crossing your mind..
Little OT, but here's another trick. When you're at the range with your deer gun fire one shot at a timeand hand the gun to a friend to reload it for you between shots. Tell your friend to hand the gun back to you without a live round in the chamber at some point without telling you. If you flinch or jerk the trigger on the shot that doesn't have a live round in it you know you need to work on it. In reality this works best when you have no idea the person is going to do it in the first place so you don't expect a dead round but you get the picture.
Good luck!