@Siebe: Do you mean: Can natural bhavanga be changed?.
No. The natural bhavnga is unchanged for the whole bhava, even for future births within the same bhava.
One cannot really feel one’s bhavanga, just like one cannot see one’s own eye (except in a mirror). But, it is the bhavanga that makes conditions for compatible thought objects to come in (through the mana indriya).
For example, when one is in a “temporary sad bhavanga state” one feels an overall sadness only because more and more sad thoughts come to the mind. One does not directly feel the sadness. When one is in a “temporary angry bhavanga state” one feels an overall state of anger only because more and more angry thoughts come to the mind.
But one CAN overcome that by forcing the mind to focus on something different. Here the best is to start thinking about the drawbacks (adinava) of continuing to be angry.
Therefore, the key point is that when one learns Dhamma, one will not be bound by bhavanga (unless one has an ahetuka birth). One can learn to be mindful and change the initial course of action that is set automatically by the bhavanga, gati, avijja, etc. While one cannot change bhavanga, one can change gati and avijja. That is why Nibbana is possible.