How to tell your boss you've got too much work
There’s something called "The Peter Principle" which says that at some point, every person rises to his own level of incompetence.
Due to your efficiency, your bosses may see you as someone very reliable, or someone who can help them solve problems that they don’t have time to fix. While the amount of trust they give you can admittedly be flattering, you still need to know how to manage their expectations, and when they give you more work you can handle, you’ll need to say “no”—politely of course.
Here’s how to handle such situations without looking like you're skirting your responsibilities:
Assess your current situation.
Every person would like to be seen as a team player, which makes it hard to decline additional work; however, you need to consider where you currently stand. How many projects are you handling? Are your tasks for the day done? How many reports have you managed to finish? Taking a look at your checklist can give your manager a fighting chance to get you on board, and at the same time, make you feel less guilty when you need to say no.
Be honest about why you can’t accept additional work.
There’s no shame in telling the truth—that you’re too busy and you already have too much on your plate. Your boss will appreciate it because you’re not sacrificing your efficiency by accepting a job you can’t give your 100 per cent to. At least you’re not wasting each other’s time.
While having someone approach you when you’re very busy can be irritating, it’s important to temper your annoyance with empathy. The person asking you to take on more work may be swamped herself, and sometime in the future, you might need that person’s help, too. Be neutral and firm with your reply, and don’t forget to be kind.
Offer some other way you can assist.
Saying no to more work doesn’t meant that you’ll stop being helpful. Ask if there’s any other way you can make things easier that’s within the scope of your job. It can still be a win-win situation for the both of you, and you don't even have to stretch yourself too thin to do it.