Managing energy

Professional athletes spend 100% of their time getting ready for events with certain events being their medium-term focus e.g. the Olympics.  They have a team of advisers, coaches, nutritionists and physiotherapists looking after them to keep them at the right level of fitness for the appropriate event.  Us weekend warriors who work during the week and train for our sport don't have such back up and we must be careful to manage our energy so we can perform at work, be there for the family and perform at our chosen sport.
Last night I ran out of energy, the tank was empty and I decided to call off my training that evening.  Not something I do easily as it could be the start of a "slippery slope" as there is always a reason not to do something especially if it takes a great deal of effort.  But I listened to my body as it was telling me, tanks empty you need a rest.  Other athletes have confirmed on facebook that "junk miles" are not worth it i.e. completing the task for the sake of it but putting in a poor performance - it doesn't achieve anything and could set you back.
So this morning I felt refreshed and went out for my 1 hour run which was tough as my tank literally was empty - I hadn't taken any fuel on board on 12 hours.  Unfortunately I can't run after taking food for a couple of hours so I ran on empty which is good practise for the later stages of an ultra endurance event, although not something you want to do too often.  When I meet my coach tomorrow nutrition is going to be top of my list as I need to increase my food intake based on the training I am doing.  It shouldn't be difficult, just need to be more aware and disciplined in this department going forward.