Mostly good information here, except for one major point: Realized gains in a qualified account such as a 401(k) or IRA do not affect your tax rate! Only distributions from these accounts affect your tax rate, and only if you distribute enough to put yourself in a higher bracket. Selling for a profit in these accounts does not affect your taxes whatsoever, which was why they were introduced in the first place...the unique lack of capital gains tax in these accounts is intended to be a carrot to encourage people to save more for retirement (since these accounts generally cannot be touched until you're age 59 1/2).

This is why I hold FITX in an IRA, if I experience huge gains I can sell to protect my profit without worrying about taxation. If I make enough to retire early, I can invoke the 72(t) rule and live off my IRA well before I turn 59 1/2 without paying any penalty taxes.