Welcome to our little corner to all the new visitors. A lot of good suggestions her and Crazy Kanga makes a good point about using the GAC "sparingly":
Because each person is different, using the GAC sparingly is different for each person too (and might even vary from day to day for the same person).
Some people might be able to get by without using it all all; just knowing it is there if they need it would be enough. A lot of people have posted in the past that they have used waiting in line as a learning opportunity, and feel comfortable doing that because they know if things get to be too much, they can use the GAC.
Some people might need it for almost every line they are in. Some might need it at MK because that place is just so overstimulating, but not at a more laid-back park like Epcot.
And some days are better than others. My DD is sometimes very bright, alert, responsive and looks like a typical kid sitting in her wheelchair. Those days we use the GAC very sparingly, if at all. Other days she's like a limp ragdoll - she has trouble sitting up in her wheelchair, can hardly support her head and when she moves or reacts to anyone talking to her, it's like she's in slow motion (if she even reacts at all). Sometimes, her muscle tone is OK, but she is so obsessed about every little thing or people being close to her that we can't be in lines. Those days we need the GAC because I can't have her more stressed than she already is.
So, if you need the GAC, use it without guilt. The only people who really know your needs are your own families.