Just a point of clarification ... euphoria basically means 'a feeling of well-being or happiness'. It has nothing to do with giggling, and it doesn't mean 'insanely happy'. Opioids, for example, are a very euphoric drug, but many of them produce almost no noticeable outward signs of intoxication except in high doses.
I'm not giving advice on this subject, all I'm saying is ... adderall is a euphoric drug, and it can DEFINITELY be abused, and habit-forming. And to almost everyone who eventually became an addict of some drug, at FIRST, it seems to them like 'this drug is what has been missing in my life. I finally feel 'normal' or 'how I'm supposed to feel' now that I'm taking it.'
So ... stick to your prescribed dose at all times, and stay in close contact with your doctor regarding how the drug is affecting you. I'd be a little worried about the fact that when the drug is wearing off you feel depressed. That is *exactly* how the cycle of addiction gets started my friend.