  We perform a constituent quark model analysis for the masses of the doubly
heavy tetraquark states $T_{QQ}$ after we fix the parameters to fit the masses
of the newly observed $\Xi_{cc}^{++}$ and hadrons involving heavy quarks
relevant to the stability of these states. We investigate in detail how the
relative distances between quark pairs vary as we change the quark content and
how they affect the various contributions to the total tetraquark masses. We
also find that our full calculations give in general less binding compared to
simplified quark model calculations that treat quark dynamics inside the
tetraquark the same as that inside a baryon. We trace the main origin to be the
differences in the number of relative kinetic energies which increases as one
goes from meson, baryon and tetraquarks. We also compare our new results with
previous works using less constrained parameters and find that the tetraquark
state $T_{bb}(ud\bar{b}\bar{b})$ and $T_{bb}(us\bar{b}\bar{b})$ are bound by
120.56 MeV and 7.3 MeV respectively.
