There was this really good Ted talk that had some stuff relevant to your question. For the life of me I can't find it right now but I'll try and get the gist that I remember.
Basically, every action has this energy treshold or whatever you want to call it that you need to push yourself over in order to get yourself to do it. Certain things are cheap and easy to do, especially if something has become a habit for you, because then it almost costs you nothing because you're so used to doing it. And as it turns out, for the average person, the biggest amount of effort is getting out of bed in the morning. Compared to that effort everything else is easy for the most part, so I think what you need to do is get yourself a list of things you want/need to do (doesn't have to be a list, just find something that you can do). Then, do them, whenever you so much as feel like not doing it, remind yourself that it requires a certain cost and you had no problem paying it earlier to get out of bed, so why wouldn't you be able to pay it again?
And no, don't feel like it doesn't count as a proper excuse, because if you ask yourself why you'll hardly ever find a reason that's actually valid. You don't feel like cleaning your room because you feel sad? Why would feeling sad have any impact on your ability to clean your room? Is feeling sad actually physically restraining you from doing it? Is it breaking your kneecaps with a baseball bat? No? Then why is it a problem? You still have the energy required, you're just spending it on feeling sad instead of being productive. Why would you do that?