What does it mean to consider as equal pain and pleasure?
Pain originates from unfavorable circumstances, and pleasure originates from favorable circumstances.
Treating them as equals means stop expecting the circumstances to be one way or the other, and being content with whatever it is. It means withdrawing consciousness from the outer circumstances of this world.
And once the consciousness is withdrawn from the world, there opens up a possibility to focus it on the inner world, the domain of the lord or the wordless word or Shabad.
And once the lord enters the consciousness, a person experiences true happiness and joy, which he had been searching outside for lifetimes in vain.