If he were the one who created the force intent, he wouldn't have to go through so much stress and pain to use the force intent to break his limits. The transition would be painless and seamless.
He would simply receive one fortunate epiphany on a random day and he would break his limits. Of course, that would take much longer. It could take decades without success.
Using the force diagram is faster. But it comes at the cost of some resistance.
His body and mind are trying to copy the intent in the force diagram, but it is not an easy thing to achieve. He needs to rile up the mana in his body with the intent and let it amplify his emotions. This will in turn help him break his limit.
When he fails to do this, the mana that has been riled up in his body will injure him. Not only will it injure him, but it will also drain him mentally and physically.
