@Stephen S, I personally think your comments were 'right on' the mark. If you don't trust the person you are with, you need to make sure you protect yourself as much as possible, even if that means stopping the bondage before it even gets started.
In personal situations (many different types of bondage partners with different experience levels), I have learned if you keep calm, you can usually explain the situation and they will make adjustments. Anyone wanting to 'rig' up another person usually has no intension of harming that person, but accidents do happen. If the partner is your SO (BF, Hubby, or Dominant), they should only have your best interests at heart and if the 'knot' is a little too tight, or pressing on the wrong 'spot', a little communication can usually help with an adjustment. Bondage is not always comfortable, but it shouldn't be down right painful... If it's done correctly, the submissive or bottom, should be able to 'settle' into their bonds in order to experience everyting else that may be going on.
A suggestion of using a safeword is excellent, but not always realistic. I was usually bound while gagged. The gag always went on first. I had to come up with signals/body language that my dominant (We had 4 wonderful years together) could 'read' if something wasn't right. Feeling safe in your 'bonds' starts with communication between both parties, and if your SO says something you are not comfortable with, you should make it known, you are not comfortable. Don't just go along with it to avoid an arguement.
The psychological part of bondage is also very deep. I have been injured by bondage scenes, I have endured long durations of bondage, and I have been bound in dozens of different positions by several different 'riggers'. I cannot express enough, how important it is to be as open as possible with your 'rigger'. You have to have a connection... a relationship... There is bondage, and then there is aftercare... You have to communicate, or things can go terribly wrong quite quickly. Also, you have to be sure your 'rigger' has pure intentions. Always discuss physical and personal limits prior to starting a bondage scene. Realistically, in the heat of the moment while having nookie with your SO, I know you don't want to stop and 'discuss' much, but you have to if you are not comfortable with it. If you do find yourself in a poor bondage situation, the best advice I can give you is keep calm, be polite, and explain what the problem is. Sometimes, freaking out doesn't help a situation at all and can actually make it worse as your body, muscles, and mind go into 'overload' (i.e. psychological damage).
Others might disagree and say kick, scream, fight... but I have NEVER found that useful. It usually only got me in more trouble because it caused a confrontational situation. This is just my experience... everyone is different.