Why am I unable to set new command prompt for terminal? Why am I unable to set new command prompt for terminal in OS X Mavericks?

I've tried to do the following:

export PS1="\u \W$ "


It works as expected but after restart the default value of PS1 will be used again. Why? What am I doing wrong? How can I fix it?

And yes, I don't have ~/.bashrc file.
Put it in your ~/.profile file.