I'm a woman and the smallest adult in my dojo, so I speak from experience: if you cannot make your technique work on a bigger and stronger person, it means that it's not good. Period. How many times have I practiced a technique with somebody my size (usually a teenager), and, just when I thought I had it, Sensei makes us swap partners, and I find myself looking at some bearded creature one hundred pounds or more heavier than me, and my technique just does not work on them. Aha! Believe me, babying a smaller training partner does not help them. Imagine what will happen when they need to defend on the street, and the beautiful technique that worked so fine on you does not work on a aggressive thug. This is the reason why Sensei will let a small person practice a technique first on someone their own size, or sometimes smaller, so that they can have the coordination for the moves. Then, switching to a stronger partner is necessary.
But I do know how you feel. Precisely because I am short, Sensei sometimes pairs me up with his ten year old daughter. I mean, I know I'm supposed to attack her, but she's so funny and so cute that I often get reprimanded for not attacking hard enough. I'm a woman, and I'm a sucker for cute funny kids.
So be nice to your smaller training partners: let them learn. That means, do attack.