Mind over matter
My sensei used the following method once:
In futari gake, the uke attack using morote dori. Both of the uke at the same time held the nage, sometimes pulling sideways and sometimes pulling the nage to the back. Basically constricting the move of the arms.
There is a third person whose job is to throw the nage a plastic cup. The objective is, the nage must not let that plastic cup fall to the ground. It starts with dropping the cup right in front of the nage, the it develops to throwing the cup short, making the nage move in order to save the cup.
The point of this exercise is focus power. If one keeps focus (100%) at what one is doing (in this case, saving the cup), without having the mental burden of being constricted, that task can and will be done. This focus and mental training is fit for everyday life as well as in any Aikido techniques.