YOU ARE ACTUALLY NOT MULTITASKING
The idea of doing more than one thing at once is actually an error because essentially what you are doing is task joggling and task shifting and not multi tasking.
Infact according to many research institutes, multi tasking leads to a 40% loss in productivity and people who consider themselves pros at multi tasking performed worse at it.
IT DAMPENS YOUR CREATIVITY
Multi tasking is a killer of brain activity. Because you do not get your mind focused on one task at a time, you usually do not give yourself enough time to understand it an unlock your creativity and be ingenious about that very task.
Your output might be good but definitely not your best.
IT TAKES UP MORE TIME
The main reason why people actually multitask is to save time but the fact is that more time is spent in multitasking than would have been consumed when taking the tasks one by one.
Multi tasking is not some special skill but an excuse to be mediocre, try the ONE TASK AT A TIME WAY and tell the difference.
IT IS STRESSFUL
Except you really enjoy being stressed out, multi tasking is not the way to go.
Your body becomes tired and weak when your brain tells it that it is weak and tired, do it does not help to literally turn your brain inside out in the name of MULTITASKING.