I just want to add something here.
I tend to avoid recording guitars via mic and speaker cabinet, until it's time to complete the song.
The reason why is that there are too many variables. You need amp, mic, speaker cabinet, guitar & even room ambience to be exactly the same for each take, otherwise you will get noticeably different results. I'll give you an example:
Tracking rhythm guitars, recorded verse, chorus, day one. come back next day to record additional sections, and the tone is off. It's not bad, it's just noticeably different. Maybe i knocked the mic. Endlessly fiddled with it, but couldn't get it to be seamless.
So, I record line in through an audio interface, and use emulation for amp heads/speaker cabinets. You'll be surprised how good they sound these days. There are even some good free ones.
Just as an example using the plugin Line 6 Pod Farm, or Helix HD on your guitar tracks removes the hassle of having do the impossible every time you record guitar. Also they have some pretty faithful emulations of a huge array of guitar amp titans.
If you're adamant that you want to record guitar the way you've been doing it, make sure you isolate your cabinet and use adequate sound treatment. It really makes a huge difference. You don't need to spend thousands, just use an old quilt/comforter and make an enclosed tent with only one side open facing the speaker. put your mic inside the tent. Also, tape the speaker cab grill precisely, so that the mic goes back in (relatively) the same spot each time you record. Snap photos of all of your amp, line in & signal chain settings, so that you can re-dial it in.
Lastly, and this may be a small thing, but personally, I avoid using GarageBand. It's not wrong to use it. It's just that there are superior and even free DAWs that will do a lot more than garage band will do.