hia,changing gear isnt always the answar, when she starts to get excited the best thing i find is to turn her in small circles and getting her to move away from your leg, and turn her in steady turns making her bend, also make sure you sit up and dont lean forward and grip with your lower leg, and dont jush haul on the reins or shell just pull back, use half hault.

    make sure he is getting enough exercise so she doesnt have too much energy stored up, and schooling esp getting her to do downwards transitions and circles, and see if you can get his owner to ride her to school her.

hope this helps, let us know how you get onxxx

I Agree with the above.

Natural horsemanship is a great help! Ground work is the key. Gain respect on the ground and build a relationship with your horse to make her want to do things for you rather than rebel.

I too used to have an older speedster pony... he was 22 and acted like a youngster, running everywhere and out running our spring chicken hacking mates!

Reverse psychology is good with this too. If i horse wants to go fast, the worst thing to do is trying to stop them as this will make them pull. By making them go fast (lungeing and riding), then they will think "i'm sick of going fast, i want to go slow now".

The same works for lazy horses... its pointless squeezing, kicking and pestering them to go faster when they dont want to, so if you make them go slower than they want to go, they will want to go fast (this tends to work with my lazy section D when riding).

 When hes first on the lunge he plays up and runs round so i let him untill he thinks "im tired of running round now" and realises im not going to give it to his tantrum untill he walks! They soon realise what you want them to do.

Good luck and remember to stay calm... this will rub off on your horse! Think positive -Nothing is impossible to overcome!

Using harsher and harsher bits and more and more equipment will not make up for your mare's basic lack of understanding of what you want or on some misplaced need to be in "control". It is better not to even think in terms of "control," but in terms of partnership and leadership. John Lyons says that partnership with a horse is a 49%-51% proposition---sometimes you have 51%, sometimes the horse does.

Safety and communication is based on the long process of developing a relationship with your horse. The relationship is based on trust, consistency, patience, and getting away from notions of dominance, "alpha" positioning, and control. 

I suggest you look into the various natural horsemanship techniques of Mark Rashid, John Lyons, Pat and Linda Parelli, Sylvia Scott, Buck Brannaman, Chris Irwin, and others. All of these trainers emphasize doing a lot of ground work to establish trust, clear communication, and desirable behaviors. Once you have those things on the ground, in the round pen, then you can get them in the saddle.

There are no short cuts. It is not fair to your (shared) horse to engage in a bit battle, when what she needs is hours and hours of retraining and kindness on your part. (At 18, she may also have some physical issues, especially wrt jumping.)

Good luck and happy relating!