I have started facing a weird problem which I wouldn't earlier.
While meditating during daytime, I sometimes doubt whether I am actually experiencing nimitta or my vittaka has waned and, instead of making way for ekaggata, my closed eyes are in fact picking up ambient light.
This inevitably keeps me from attaining stable anapana-nimitta in that session and the progression plateaus, irrespective of how effortless maintaining concentration has become. That leads to restlessness and I either don't feel like keeping my aditthana, or if I can nullify that I emerge from the session somewhat disappointed that I didn't utilize the session well.
I'd like to clarify that I not seeking any jhanic factor or for anapana-nimitta to emerge, and I can attain anapana-nimitta and subsequently absorption for desired time period before progressing to the higher jhanas during night-time because I know I can't be confounded by ambient light...
So, other than only sitting at nighttime, which isn't really a solution, what do I do? Any pointers?