In space you could accellerate forever .
But as you gain speed it requires greater power to accellerate further.
As you get close to the speed of light ,the power requirement becomes rediculous.
At the speed of light the power requirement for further accelleration is infinate.
This is the effect of "increased mass".
Also as one gains speed the passage of time is affected at the speed of light time would not pass any more.
On the other hand there are Tackyons
http://www.gallup.unm.edu/~smarandache/Russo-faster-than-light.pdfAnd warp drive , which would move the rest of the universe without accellerateing you so much.