It is important for all athletes, equine and human, that you have variety in your training programme. Firstly it is good for your muscles and general biomechanics to vary the way they have to work. Always keep in mind that you have to work for strength, control and endurance and this is why variety is necessary.
People and animals become bored with the same routine every day. Cross training has always been absolutely brilliant to train different elements of fitness. If you are unsure about what you can or should do extra, contact a professional and find out what you options are. Physiotherapists will always to able to advise on what kind of exercises will be good for human and animal patient.