I don't know but I've felt more able to try either first thing in the morning or last thing at night. I tried the Nighty night this morning and have done again this afternoon but the attempt this morning seemed to be easier to just try without thinking.
When I OD'd last year, I was very tired at the end of the day and had been considering it for a few days and just thought 'f it' just do it. I could barely keep my eyes open while taking the tablets, because I was so tired.