What is the ruling on repeating phrases such as: "So-and-so will only deal with me according to what is written in the Preserved Tablet," and similar expressions, while feeling that what emanates from people is in accordance with what Allah has decreed? And is this considered to be from the doctrine of the Jabriyya?

Your belief and repetition of those words to yourself are not forbidden, nor do they fall under the doctrine of the Jabriyya (Fatalists). The correct belief is that nothing occurs except what Allah has decreed, while man remains responsible for his actions, which he performs by his own will and choice. As for the Jabriyya, they deny the will of the servant and believe that they are compelled in their actions.