Our character is slowly formed in many lifetimes and because character traits reincarnate we do not have to start over in every life. Only in this way can we build a strong and especially loving character.
Source:
-We see arts and sciences again, madam, as a result of our emotional life. We built up all our characteristics as a result of many lives. And that goes slowly, we learn almost nothing in one life. At least for the good.
Question and Answer Part 1 p.88
-If you love the life, then that character and that personality will come of their own accord.
Question and Answer Part 4 p.385 (Q4.16330.16333)
-I can assure you that there is material inheritance. However, not for the soul!
What does that mean?
That the soul is not given any thoughts or power of feeling for its life on Earth.
Mask and Men p.858
Quotations from the books of Jozef Rulof
See also: https://rulof.org/Our-reincarnations.html