How much do our previous incarnations affect our current one?

[anagogy]

Could the positively-polarized entity in one incarnation easily turn negatively-polarized in the next incarnation?

There is always this possibility...however, polarization implies consciousness or "awakeness" or "awareness". The more polarized you are, the more conscious you are, so if polarity is switched during an incarnation it is likely not to be a willy nilly random choice, but a very deliberate change in orientation.

Also, everybody wobbles on and off the path occasionally, from life to life. Your violet ray emanation or overall expression of self-hood is a signature from more than just one life. You could, potentially, be very negatively polarized in one life, and your "overall" violet ray polarity could still be positively polarized from your other positive lives.

Or is there a metaphysical predisposition that makes us more likely to a lean a certain way every incarnation?

In the same way that there are genetic predispositions, there are spiritual complex predispositions. You could probably consider that a metaphysical predisposition. The spiritual body and mental body are just as "real" and influential as the physical body.

Are our personalities likely to be similar from life-to-life? If so, where does such an effect come from?

Again, just as the body has various genetic predispositions, there are mental predispositions, and spiritual predispositions. The mind, and spirit, of course, do not die with the body, so those dispositions carry over from life to life to some extent.

Do our environments and choices in each life solely shape us?

No. They do play a part, but also consider that the environment, and body that you incarnate in are also a reflection of your choice, or expression, as a soul. In the same way that John Doe wears leather because it expresses his personality, we choose lives, to some extent, that "reflect" our essential character as a soul personality.

Or is there a likely influence from the past in each incarnation?

We are influenced by the past, present, *AND* future. From a spiritual standpoint, you would do well to just consider all three of these influences as "present".

How does this influence exactly work?

The conditioning and modulation of consciousness. In other words, distortion.

Good questions.