Hey Jared,
First of all, many thanks for this thread!
I skimmed through it, and saw an earlier post wherein someone talked about losing interest in their current pursuit as soon as they had become "good" (but not great) at it, and thereupon moving on to some other project.
I have similar issues, and would say that your characterization of this poster as a "jack of many trades and master of none" applies to me as well. I'm pretty sure I've thought of myself in those exact terms before.
Looking back, I can see this has been a pattern in my life. I'm curious by nature and derive great enjoyment from learning and trying new things, but the problem is it's often at the expense of abandoning old things. I've waded through more hobbies than I can remember... piano, calligraphy, webdesign, programming, arts 'n crafts, Braille, cryptography... When I develop an interest in something, I'm driven to great lengths to research and learn it. For that period, it consumes my mind. It may cause me to be negligent of some of my other responsibilities. However, this passion for any one subject has rarely been sustainable, and rather, proven easily displaced by new subject matters that catch my fancy. Once my passion for a field diminishes, so does the effort I make to pursue it. As a result, I'm decent at many things, but not excellent at anything (i.e. jack of many trades, etc.).
I even see these tendencies manifest themselves within poker to an extent: I move from variation to variation, format to format (it's 6-max PLO Cash one day, Full Ring NLHE another day, SnGs the next, Stud 8 on Friday...), and I'm afraid it's preventing me from maximizing what I can get out of any one game (and by extension, from maximizing my profits).
As a kid, it was okay to dabble. To follow my whims. To have superficial knowledge in a wide, unfocused array of subjects. But now I'm at a stage where I should be buckling down and "specializing". I don't want to lose my basic enthusiasm for learning, but I want to redirect it.
This is how I've formulated in my mind what I want to change about myself: I want to stop being so passion-driven, and start being passion-driving. I want to be in control of my interests, rather than have them be in control of me. What steps do you think I could take to start working towards this?