People quit benzodiazepines and barbiturates after years of use and with time get better. I'm not too familiar with the pharmacology of phenibut, I'm not sure if it's well understood, but it's either a GABA agonist or a gabepentionoid, or both. When I quit benzodiazepines after 9 years of daily use, I was slowly recovering for 9 to 12 months before I could say I was close to baseline, but the most intense phase lasted for around 3 months, I guess, with nightmares, extreme dissociation, anxiety, and tremors. Mentally I'm sure I still experience effects from long-term use over 3 years after quitting, but a one-two-month use is really nothing to worry about long-term, the withdrawal effects you describe are classic withdrawal effects from GABAergics that everyone experiences even after short-term use without weaning yourself off.