Why can't I say 'No' to my boss when I'm buried under work?

Saying "no" to your boss is intimidating because they are your superior literally. You don't want to upset the hand that feeds. But you can communicate with your boss, share your feelings and you guys can come to a compromise.

Because you may feel like you will be judged harshly by your boss as being inefficient, underperformer etc. It's better to try and negotiate your workload to a standard that is acce ptable to your boss and that you can cope with. You can try being assertive and politely negotiate your work priorities with your boss.

Maybe you don't want to let him down and that isn't a bad thing but you should remember to take time for yourself because that's important too. It's ok to say no and your boss isn't going to think less of you if you have to say no sometimes. Im sure your boss will understand and will already see the work you put in. If you feel as though he/she may feel let down by you saying no, you could explain that you are already loaded with work (which i'm sure they will already know). Taking time for you is important so don't forget that

I think I can't say "No" to my boss to show him or her respect in workplace. He or she was the one who hired me and promised to give service on the company. It is inappropriate to reject a work he or she is assigning to me. Though, buried on work, we must accept and continue to work for the company. However, when we can no longer handle the tasks we are assigned to do, it is okay to take a break and tell your boss what you currently feel about it. He or she needs to understand because the welfare of his or her employees are important too.