Dude, don’t be so critical of yourself. That was my problem also. You are not helping yourself, you are just putting more pressure on yourself and backing as a new guy is pressure enough.
Half the veteran drivers just park at the entrance, fuel pumps or CAT scale and don’t care if the truck stop burns down around them or they shut down all interstate commerce east of the Mississippi. You are learning a new skill not trying to learn how to use a bucket. Your school probably did very little to show you and pushed you toward the DMV.
If you can make a diagram or post a pic or example, it may be easier to help you. When you are driving down the “road” of the truck stop in front of this angled parking, is your tractor’s driver or passenger door closest to the empty parking spot you are trying to back into? Most of the spots dedicated to the Idle-Aire service expect you to nose into the parking or require a blind-side back and that’s more difficult for everyone.
Just remember, you are learning a mechanical skill. There is almost no reason you would already know how to do it anymore than a kid raised in the city would know how to tie 15 different knots in a rope. Even watching a video a couple of times would not be enough. Until you tie the knots, step-by-step, you won’t REALLY have learned it. Then you have to practice tying the knots, one at a time, and over and over and over until you can do it without thinking very hard of each step. I worked for a flight school. It takes a good teacher and a willing student, and a GOOD step-by-step procedure and then almost anyone can learn any skill. I doubt you’ve had ANY teachers in trucking that are very good and each one probably had some sloppy and rushed folksy way for every skill and it was mostly “come on, do that thing NOW, oh heck, no. Now, turn, turn, STOP!!!!!”
Essentially all truck stop parking is a 45 degree or a 90 degree back and most are on the driver-side. Watch YouTube until you find a video that makes sense to you and watch it over and over until you understand it and can find where the tractor drive tires and the trailer tandems are when the key steps are started or where they should be when you are doing it. Someone need to show and tell you what to look at, when to look at it, how to judge if that thing is too far left or too far right of where you want it. And then you need to be shown and practice how to correct for too far left/right. LOTS of veteran drivers still correct in EXACTLY the wrong way when the trailer is too far left/right if where they want it.
One thing to think about, it helped me, but it may not work for you. Imagine you are already parked in the spot. Now imagine driving straight out of that parking spot toward the setup postion you would use to begin baking into the spot. Visualize the steering commands you would make while driving forward. Write them down it you have to or just remember them. There are dozens of ways to teach or explain the method. You can always sit somewhere and watch other drivers park in spaces if you ever see that happening instead of the guys just noseing in or parking along the curb at the truck stop entrance. Those guys should have their CDL suspended in many cases.