Well all the above is very good advice.

But a wise man once said "A Zero is better than a Hefty Bag"

In other words if your off by 45 degrees which is really easy to do when first flying a Double Immelmann. Sometimes you will be better off using the next manuever to get back on line and your bearings.
anyways as an example and using the double i as an example seeing as it is a center manuever.
If you really get off line you can use the end of the box to get back on line and possibly zero that manuever but at least when you get back to center the next manuever will start out ok. if you fly past center while trying to correct from the previous manuever they both get zeroed.

And especially in Sportsman no one makes it unscathed in their first contest. Usually nerves, a different field and not to mention judges and trying so hard. By the second and third rounds you will start to become relaxed enough to stealth in the corrections. I am trying to teach a perspective new pattern flyer at my club. and a couple manuevers that i did not think would be tough are.
mostly the vertical upline. entering this manuever straight and level is the key as you cannot tell if it is drifting left or right.
whoever dreamed up the cobra. An easy thing to do. the key is the half cuban eight. if it is done to big no time to do the cobra and center it. not to mention if the half cuban eight comes out crooked.
tough manuevers to do
the double immelmann entering it with the wings not level usually leads to the wrong rudder on top when the plane is inverted.
the two inside loops tough enough on a calm day much less with a crosswind or even one straight down the runway.
the two point roll usually holding down while it is inverted and then holding down when rolling out. tends to pull the plane off line and leads to a nose down condition on rolling out.

Anyways have fun and i hope to see you at a contest.