Pride listened to the question, pale grey eyes regarding Aster thoughtfully. Weak though he was, he knew that this would be better-explained directly mind-to-mind, and so he tried--without much hope in success--to reestablish the link between them.
To his surprise, the link not only reopened, but it did so strongly, smoothly, and he found himself accidentally broadcasting Aster with his startled delight. What a treat! The moment he realized this, he quickly got ahold of his thoughts, gathering and organizing them. He'd done this for communication, after all; best to communicate for as long as he could keep the link open.
This link will fail, in a moment, but let me open it to show you the answer I was given, when I asked this same question, in this same place, not long ago.
He sent images, sounds, words. Not all of them he had at the time understood, but most, in hindsight, he did. In the imagery was Pride, the same little white fawn that stood before Aster now, unchanged. Reseda crouched before him, looking as thoughtful as a lizard could, as she spoke.
"I...do not know this. It is simply something that happens. Perhaps magic is simply unpredictable. Perhaps our hearts are not into it. As you practice and grow, however, it becomes easier to succeed. There is more success than failure, but there is still a chance the spell will not work." Her voice, in the memory, in the thoughts that Pride struggled to transmit, was a distant and strange echo, touched by thought and emotion--his own curiosity, his own attentiveness, his determined intent to learn more. To improve.
Reseda, in the memories, continued. "Magic of the mind is more difficult to master then our native energy. It requires focus, will, and a sharp mind. Even now, I struggle to learn new spells from this element, but they are useful and powerful. Focus your mind, change your element from the core. Release it, let your will pass through."
With that, Pride looked to Aster. This is what I was taught. I cannot hold the link open any longer, though I hope that this aids you, as well. If you do not understand it all--remember it. I did not understand it at first, but now I know much more than I did, though it has not been too long. Also-... I do not know how right she is. I believe she was making an... educated guess? At best. It is what she believes, but it may not all be true--and it may not be true at all.
He paused, glancing up at the Spire. This place, too, makes things stronger--but more chaotic. Harder to hold onto, I think, but good for learning control. Perhaps if you want to learn how to... merely use a magic, it is best to do it somewhere... less... He sought for a word, but realized abruptly that the link was slipping shut as he did so. He looked to Aster, blinking pale grey eyes.
"Less... volatile," he finished, dredging the word up from some half-forgotten memory--and just as he imparted the meaning to that word, the link between them began to close.