Something I have observed in a number of communities where reincarnation and conscious memories thereof are accepted is the tendency to confuse last time with this time. This seems to be particularly accute in the otherkin communities where past incarnations become the basis for identity in this one.
Whilst who you were can, and for some people does, have a significant impact on who you are now there can be serious problems with mixing the two. It doesn’t have to be anything particularly psychotic-looking (though I’ve seen a few of those too).
Many people have encountered “elven princess syndrome” wherein someone tries to carry over status from a previous incarnation into this one, but the most common one I see is relationship propogation.
It’s actually a joke in at least some pagan circles, having been overused by somewhat unscrupulous people that “we were lovers in a past life” is a classic bad pickup line. Well maybe we were, but perhaps this life the only interest I have in your genitalia is to tenderly wrap them in a wasps nest.
Part of the point of reincarnating is to be someone different. To do new things, learn new lessons, have new experiences. Not just to replace a worn out body so you can do the horizontal mamba with your dearly departed from. Sometimes that happens, but only because the people you are now are compatible in that way.
To use a personal example, there is someone I know in this lifetime that I have known in others. Yes, she and I have been lovers. We have also killed each other from opposite sides of a vicious genocidal war. Which of those roles should we bring forward into this life? Well, neither, we are not either of those people anymore.
The same can be said for any other trait. If you were a psychopath last life, it doesn’t mean you are now. Nor that you should necessarily wrack yourself with guilt over it. Learn from what you remember, make yourself into a better person. Sometimes the lessons aren’t what you think they are. That’s part of the pleasure of life.
And yes, this applies to species too. Because you were something in a previous lifetime, that does not mean you are that thing now. Maybe there are traits that you can bring forward that assist you in this lifetime too, maybe there are enough traits that you consider yourself the same sort of creature. Maybe not.
If you are going to actively draw traits from the past into the present then choose the ones that benefit you now. Also remember that whilst your affections may have been truely undying, the object of your affections may be learning this life’s lessons from being that psychopath, or simply from loving someone else.