As an example, let's say you have a medical condition requiring you to take medication every day for the rest of your life. You can't count how many days you will live, because you don't know how long your life will be, and that is why I would use 'every'. 'Every day' has no limits... it blanketly refers to every possible day that will ever be.
But now let's say you have a short-term medical condition that requires a course of medication. Your doctor may give you a pack of 7 pills and tell you to take one each day for 7 days. The days in this course of medication are limited, they can be counted, and that is why I would use 'each'. 'Each day' refers to the days in the course.
To sum up - "every" can be used without limits to make a blanket statement about every possible instance of something that has ever been or ever will be. "Each" is for referring to things that can be counted or numbered. It can still be used for future possible instances, but as it emphasises the individuality of each instance you need to be able to account for them to know that your statement will apply to them all.
In my answer to your previous question about this, I suggested that either could be used in your specific example of solar eruptions emitting radiation. Your choice would depend on whether your statement was a 'rule' without any limits, or whether you were narrating a limited period of observation in which the eruptions could be counted.
In your new example, it could also depend on the scope of your statement. When you say "every decision in life" are you just talking about just your own life and perhaps the life of the person to whom you are making a recommendation, or are you talking about the life of every single person that will ever live? Are you talking about just major decisions such as your education, your career, or your relationships, or are you literally referring to every little decision you make, such as what time to get up, what to have for breakfast, which route to take to work etc? If you can account for everything within the scope of your statement, 'each' might be fine; otherwise, I would go with 'every'.