Something I've noticed in the past few years and have been paying attention to is the point in training (or real life) where uke has stopped being the aggressor and I, with the thought in mind of 'doing the technique', become the aggressor. I've been focusing in my training to recognize when the attack is over; I believe this has helped me in two ways.
1) As nage I am more sensitive to the shifts in uke's body/mind. I'm not frustrated (as much) by forcing myself to reinitiate an attack that uke is no longer putting juice into just to practice something which isn't real or happening. Overall I feel more calm because I can respond to the moment--to me the heart of aiki--sensing when conflict is deminishing or over. I learned how to let things go a little better. When I can let go I have choice; when I have choice I have freedom. I give a gift of understanding to uke.
2) As uke I now give continuity in my attack to nage, never quitting at some point (which I used to do and think many folks still do)so that nage has to create an attack for practice where none no longer exists. This has enchanced my overall practice because by staying connected and engaged with nage I can learn to feel where their 'holes' are and sense in myself what I would do to counter them, without actually doing it, just visualizing. I learn more from nage when I engage more as uke.
Just some thoughts. Take care all