The "happy and relaxed" is the nicotene settling in; like the buzz from good wine, that is not strictly why we follow this, but it's a not altogether unpleasant side effect. Also, the act of smoking itself is calming and meditiative, the cadence of the draw and the reflection on each texture, taste, and aroma, so the act of pipe smoking in itself can have that effect.
The mania to aquire, learn, and absorb as much as possible as quickly as possible, is the aforementioned PAD and TAD. As I am one year in on my serious pipe journey, and already 30ish pounds deep, i feel you on that! Keep it in perspective, and in budget, and you're good; just like anything else, if you enjoy it and it isn't obstructing your real life and your relationships with family and friends, it's all good. o)