Realize that in the same way that you can stop and correct the diabolo, you can perform your tricks in a way that you can tilt the diabolo (in fact that is why your diabolo changes position when doing tricks) so just try to execute the suns with you left and right hand in different positions and see how the diabolo turns in one or other direction.
After a while you will see that you are able to perform these kind of tricks not only keeping the diabolo in the correct position, you will be able even to accelerate it.