Thats why you need to store the state which is the last read position as stated here: https://developer.adobe.com/app-builder/docs/resources/journaling-events/lesson2/ 

Alternate I could think is, create as non-web-action using alarm. And cron trigger the action every say 5 mins. Is this correct that "Reading journal events must be created as non-web-action using alarm cron?" This is correct.It can be a web action too using an alarm.Please refer to https://develope...