Upvote:3
There's no problem. If they call to board group 3, for example, anybody in groups 1, 2, or 3 can board (but not people in group 4 yet). So if you miss your boarding group, you can just join the line and board with any later group with no problem.
The worst-case scenario isn't bad at all: if you get in line too early (say you're in group 4 and they're only boarding group 1), you may be asked to step out of line and wait when you reach the front. So even if you make a mistake, nothing bad will really happen.
Note that you must be at the gate 20-25 minutes before departure, so don't plan on showing up at the very last minute.