I think that you may be asking the wrong question. Unless your job is to punctuate someone else's writing without changing any of the words, your main responsibility to readers is to say what you mean coherently and accurately—not merely to say it in a way that you can justify on the basis of some theory of punctuation.
Commas are extremely flexible punctuation marks and can be useful for everything from demarcating major divisions between clauses to indicating parallel words (or word groups) to signaling a natural pause in speech. But overloading a sentence with commas negates their value as signals. Instead of helping readers follow the structure and flow of the sentence, the comma glut obscures the relationship of the various words and word groups to one another. Readers then have to stop and try to reconnect the disjointed pieces of the sentence. Or they stop reading.
As an experiment, I reworked your example twice—once retaining all of the original words but repunctuating the excerpt in an effort to make it read as coherently as possible, and once treating both the wording and the punctuation as subject to alteration. Here are the results.
Changes in punctuation only:
I think sometimes that my use of commas and, occasionally, exclamation marks can be excessive. Whenever I add a word or expression not necessary to the sentence, just like I did with the "not necessary" and like I am doing right now, I always include these words—well, maybe not "always"; "usually" include these inserts—between commas. So, basically, I enjoy writing long sentences joined with lots of commas and (frequently) semicolons and (often) colons—and have been rather prone to using brackets, as well.
When writing lengthy, detailed sentences, I find sometimes I can get carried—or at least I think I do—and can join two, three, or sometimes more usually related but separate ideas that could be separated into individual, perhaps less interesting, sentences.
This version of your original writing still suffers from a couple of lapses into incoherence that no amount of fiddling with punctuation can solve, which leads us to the second revision.
Changes in punctuation and wording:
Sometimes, I think, my use of commas and exclamation marks is excessive. Whenever I add a word or expression that is not necessary to the sentence, as I might have done with "not necessary" and as I am doing right now with this longwinded aside, I always (or usually) set off the words with commas. Basically, I enjoy writing long sentences and punctuating them with lots of commas, as well as with somewhat smaller helpings of semicolons and colons. I have been rather prone to using brackets, too.
When writing lengthy, detailed sentences, I sometimes get carried away and find myself joining two, three, or even more related ideas that could be separated into individual (though, perhaps, less interesting) sentences.
As the second reworking suggests, many of the commas in your original version were serving not to "join" related phrases, but to accommodate extraneous verbiage. Most writing that aims to communicate effectively with readers, rather than to display one's real or simulated stream of consciousness, resolves itself into coherent parts without intervention in the form of overwhelming punctuation.
Best Answer
Although both are independent clauses, a colon is the more appropriate choice here because a compound list follows the initial proclamation and serves to support its assertion.