A lot of it has to do with your programming. If you are training for 3-4 hours a day, 5 days a week, you have a great potential to do too much. Here's the deal:
- Overtraining is accompanied by a loss of performance, and in more serious cases can be accompanied by symptoms that look like clinical depression.
- MMA fighters and military are not training anywhere near their genetic potentials. They are focused primarily on conditioning and skill training.
- The closer you get to your genetic potential, the easier it is to go from the training stimulus needed to overtraining.
If you are a weightlifter, then the response to overtraining should be:
- Reduce volume of work for a while (about 2x as long as it took to get into the overtraining state)
- In serious cases, take a layoff for a couple weeks before slowly coming back on line.
- Look at your programming really hard. You have to manage training stress, life stress, and recovery.
It may be worth splitting your 3-4 hours up into a couple sessions. Even when you have that amount of workload, you should have cycles of intensity, effort, and rest. For example, after a high intensity or a high effort session, you should probably do a lower effort session.
With a better description of what you are doing, it might help in troubleshooting the programming.