Hey soyeso i can amagine how frustrating this is for you to see your beloved pet so distrought over something so simple.Some confidence and distraction training would be just what the doctor ordered i dont know if you are expierenced in dog training but the actual training is very easy its a case of distraction from the actual issue to make him/her comfortable in the situation and when you find that distraction ( everyone has a different method to best suit their pet) basically you keep repeating the process and they will come round it all depends on your own motivation to stick with the training. Dogs live in the now its funny cause i had the exact opposite problem i had a golden retriever who would go to any length i mean any length to catch any flying object that crossed his path it became a problem one summer when he went for a nasty sized wasp which in turn stung him at the back of his tongue he had a bad reaction and almost died thankfully he didnt the reason that is am telling you this is i suspect this is what happened to your pet obviously without the bad reaction but it obviously caused him some distress ( poor thing ouch

) I am a professional dog trainer and i love it i hope i helped you in some way let me know if you need any other advice and ill help anyway i can