If you are shooting for a 18-19 hour fast that means in a row. So you'd fast, eat from 1pm to whatever...depending on if you were going to fast the next day as well. For example.
M - normal eating day last meal at 8 pm
T - fasting day so you fast from your last meal on Monday for 18-19 hours, so you eat at 2 pm - 8 pm
W - fasting day so you eat at 2 pm - 8 pm
Th - normal eating day
"And for crying out loud. Don't go into the pain cave. I can't stress this enough. Your Totem Animal won't be in there to help you. You'll be on your own. The Pain Cave is for cowards.
Pain is your companion, don't go hide from it."