NO! IT'S A TRAP!
Seriously though, don't think this way. There is nothing rude about stopping when you're full. Eating to make other people happy is crazy and part of what got us here today. Wash that thought right out.
Coping mechanisms: get smaller dishes. Eat with chopsticks. When going out for meals with friends, angle to make it a family-style restaurant or tapas place where everyone eats from communal dishes. If you do go to a meal-per-person place, aim for the soup. Ask the server if you can have their salad mains served as a side salad instead.
And if all else fails, just don't care. Eat the five bites and when your colleague looks at your plate and asks if you didn't like the food, tell them you got hiccups halfway through the meal or got so focused on talking and now you're going to bring it home because you want to finish it later. They won't care past that unless you actually look sickly.
The one exception I make for this rule is if a family member or friend is cooking for you in their house. In which case I make sure to tell them up front I'm not hungry/ate a lot beforehand/don't want to eat a lot, but that I do want one bite of the dish they slaved over. And when I eat that bite I make sure they know I loved it - most people don't care whether or not you ate in quantity, but that you appreciated the quality. So the compliment matters more than leaving a clean plate. If the other person is paying for your meal, tell them up front you plan to order lightly but deliciously and again, compliment and thank.
I've also had a devious amount of success tasting something, saying "oh, this is so good! try some!" and then getting other people to snag bites off my plate. Magically disappearing food!