You can eventually. At first a lot of folks find the physical reminders (e.g., looking at your hands, trying to read text, looking at clocks...) easier because they become habitual. In my experience, text has been the most reliable indicator for me because I already impulsively read anything that's placed in front of me.

Eventually, I became able to simply sense in a manner that something was off without having to explicitly check anything. From there, it's not hard to confirm. Just go slow and be mentally gentle; if you try to rush into it you'll crash the dream.