One of the things about past lives is the issue of accuracy. A fair portion of "past life recollection" is simply what we want it to be.
It is entirely possible to have a "recollection" so vivid that you can feel the mud squishing between your toes, smell the animals, and feel the heat of the sun on the back of your neck. Then you look down and see that you are wearing a cotton shirt. The downside to all that is in the early 1500s Europe, when you "think" you have regressed to, the chances of actually wearing cotton and feeling mud between your toes at the same time are slim to none. If you were smelling animals and feeling mud, you were likely a peasant. Peasants didnt wear cotton, they wore linsey wool. Furthering that, tunics, not shirts, were the "ordinary" fashion of the day, not shirts.
See where I am going? You can use identifiers such as that to validate your "regressions" and usually you will find that they are false. Now, is that to say that having a past life regression is always going to yield false results? Absolutely not. Just be aware that especially ones done on your own very likely can be a nice trip through a vivid imagination but not much more.
Just "feeling that it's SOOOOOO true and real!!" doesnt make it real, it is the least accurate method to use. There are markers of accuracy, though.
1) Find a calendar or some sort of time marker.
2) Are your clothes matching the time period? Not in style because thats relatively easy if you have the least knowledge of the evolution of fashion, but material and construction?
3) Does the architecture and environment actually match? For example, if someone were to state that they see corn growing, just outside European castle gates in the 1490s? Europe didnt have corn at that time. See where I am going?
4) Language. Does the syntax and style match? Do you understand it? If you're wandering about Athens in 1786, you're not speaking English.
The brain, being the powerful tool that it is, can conjure up the strongest feelings imaginable. However, that does not make them accurate or true.