Razal said (Menahoth 44a) that one who does not wear Tefillin transgresses eight positive commandments every day. This is because there are four Parashioth each in the Tefillin of the arm and of the head, and each one is a positive commandment, making a total of eight.
On the other hand, one who wears them every day fulfills eight positive commandments. Additionally, one who is particular about wearing Tefillin will have the scales tipped in his favor on the judgement day, but one who was not will find the scales tipped against him, Heaven forbid. Rabbenu Hayyim Wittal, 'a"h, cautions about the severity of not fulfilling the commandment of Tefillin.
As such, it behooves every man to be particular about this important commandment and he will, as a result, merit to receive all the good of this world and of the world to come.
(See Q.Sh. 'A. H"R Rafael Baruch Toledano, 32, Oth 3)
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