why we can not reach to the light pace?

Answer 1

Because we are made of mass (or matter).

It would take an infinite amount of energy to make substantial amounts of matter travel at the speed of light.

i.e. E = m c^2, therefore c = Sqrt (E / m)
The more mass there is the more energy is required to accelerate the mass. Also as you get faster and faster, your mass increases - meaning that now even more energy is required.

Only massless EM Waves i.e. Photons can travel at the speed of light 'c'.