
Fully prepared for action; also, spoiling for a fight
Fully prepared and eager to initiate or deal with a fight, confrontation, or trouble
Prepared to deal with attacks or criticism : prepared to fight or argue

Above are just some definitions for the phrase “loaded for bear”. At times, you will see riders get on unknown horses doing precisely this ; loaded for bear.
What this means is that instead of waiting to see what the horse can and will offer, they are already preparing themselves for a battle. Normally it is a battle with the horse’s head.. to force the horse’s head down in the first 5 minutes of their bums touching the saddle.

In non-horsey terms, it is like walking into a room and yelling at your child / mother / husband / colleague from the first word, instead of trying to have a normal civilised conversation.
What ensues is a horse that gets more and more tense, and a rider that is getting stronger or more frustrated because the ‘bloody horse’ is not doing as it is told.
A better way of doing this would be to check that you have brakes and a go button, and allow the horse to walk around on a long rein to stretch his muscles and to warm up. Decide if you are just exercising the horse or if you are actually going to school it.
For the first ten minutes or so, see what the horse can or cannot do, what are his weak areas and what he is willing to offer you. Then start making adjustments and changes, according to both his and your ability. If the horse you have just gotten on is a 16 year old riding school horse, you may not make him into a super supple horse in one session, but you can improve his suppleness. If he is an ex racehorse 3 months off the track, he may not have a great mouth (yet) but you may be able to improve the contact in this session, or work on something else that will improve the contact.
Whatever you do, don’t get on an unknown horse “loaded for bear”. Give both the horse and yourself a chance to get acquainted with each other and see what each side has to offer… Try it and let me know what happens.