Re: Instructor got mad because I didnt fall
I agree with the comments made by Lynn and David Yapp. Sticking to the original problem, I too have faced this on numerous occasions.
When I first began the study of aikido, I knew nothing, as all of us. I quickly learned that aikido is not a strength contest. The techniques do not require a great deal of strength and the use of it is a measure of error. However, I also knew that the principle only went so far. I knew I could, if I wanted, force my way out of some things if I wanted but from previous martial experience, I also knew that the purpose of taking ukemi is to learn how the technique works and how to fall out of it safely. So, fighting the technique of nage to a point is not product and can be considered as horse play.
How I view and handle this situation in practice is, when sensei is giving demonstration, he is trying to teach, NOT PERFORM. So, be cooperative in getting the instruction across. There is a difference is instructing and performing. When in group practice, you have to gauge the skill of the partner. If you know someone is not as skilled as you, the don't resist as if it were you being nage. Let down your guard a bit and assit in making the technique smooth. Resisting with prejudice against someone inexperienced will not help the nage learn and could lead to an accident or injurry.
However, when you are uke for a capable nage, by all means make it real. In times past, even for sensei, I would roll out of things and allow the technique to progress when obviously I could have resisted. Knowing, that I am unusually strong, I was aware that resisting to the point of showing up sensei was both unfair and disrespectful. So, I resisted enough to give him a good work out but I did not go overboard and appear that we were in a cock-fighting contest. Also, strength works if you know what is comming and know how to deal with it. The average strong person on the street will not know what hit them. So bear in mind, when performing uke responsibilities, attack with the mind of someone on the street that has no knowledge of aikido but fall out of the technique as an aikidoka. Did I sound confusing?