You can't always plan what happens out of your control. Timing won't always be on your side so it's important to improvise when you least expect it. Sometimes we have that open window for an hour so we train for that hour. Don't be discouraged because you won't always get the time in to train. People get so worked up at times that they forget that they actually did something instead of nothing. It's one of the reasons why I like training periodically throughout the day where when I have a few minutes i'll do a few exercises to stay in my realm. I normally don't go for more than 30 minutes unless i'm doing qi gong and time passes by without knowing it, it has happened on occasions.
When you feel completely wired up and need a way to chill out, go do what you need to do; hit the gym, go hard on animal movements, do sprints, lift rocks if you have them, practice Hand Balancing whatever you feel is right to get all that energy out of your system. Kids especially could do some crazy training not to push them to the brink of ultra exhaustion but to give them that release so they can focus and be alert in a calming matter. If your energy levels are low and having low-self esteem, fix it any way you can that is productive and positive; its tough being motivated when you're low on energy but you have choices and possibilities.
There are ways to learn on how to stay efficient in your training but at times it can hit you like a bolt of lightning or it may not be enough. If you train too long more than you need to, it can drain you and leave you fatigued & aching everywhere that isn't necessary; however if your training is too short that you're not feeling anything or you don't feel it hitting the spot, the results may not be coming and it won't be enough for your body to get into that hormonal stage. Do what's comfortable for you but do enough to where you feel satisfied, not broken down or feel like things aren't going right.
Value the time you have the opportunity to use. Find your range of time and use it the best way you can. You won't always be able to train at a specific time because time doesn't stop just so you can get a workout in. Make it a habit to say "whatever time I can use, I will make the best of it." Don't expect to able to train every single day for an hour straight unless you're actually in a sport otherwise things pop up that are out of your control. Learn to use the time you have to get what you want out of it.