Valentin is right, the hours you are speaking of are not excessive and quite normal for a gymnast of your level. Do you ever wonder why some people cope with the hours better than others. It is often the things you do outside of training that affect how you survive training.
The number one key factor is generally hydration. Dehydration is the number 1 cause of fatigue, most people are not even aware that they are dehydrated until it is quite serious. You need to be drinking lots of water during training, generally a small amount of water should be drunk every 15 minutes of exercise as well as before and after training. But even more so it is important to keep hydrated when you are not training. Your body is 80%, if you drop by even 1 or 2 % you concentration and energy levels will drop significantly.
Speaking of hydration the biggest problem in most people diets today is in fact not what they eat but what they drink. These days it is common to consume lots of cola, soda's, fruit juice, energy drinks, alcohol, coffee and hot chocolate. These drinks were all designed to be consumed occasionally and many people consume them daily. Some people even consume them multiple times per day. If you are one of these, cut this out and you will find a huge difference to your energy levels.
Your diet is of course of primary importance. Poor diet will cause fatigue, lack of energy, less concentration, sluggishness and so on. Most people do not even realize that their diet is doing this to them because the wrong foods are consumed so often that the results are considered normal. An athlete like you must avoid junk food and take aways, too many processed foods and candy.
The other big issue is screen usage. At night time your body produces and chemical called melatonin, this chemical relaxes you body and allows you to sleep. Screen time reduces this chemical in your body this includes Television, computers, video games and ipods. When you have trouble producing this chemical you don't sleep as well and you become over tired. This will build up, someone who is even just a little over tired has the equivalent to a 0.05 blood alcohol level. I wouldn't want to be doing gymnastics like that.