It's important to consider the purpose of suffering because if I'm not careful, my pain and grief can take me in a direction I mean not to go; worse yet, I may end up in a place I do not desire to reside, unable to return.
One of the biggest reasons why I've come to realize I've been allowed to suffer (yes, allowed) is because it gives me an opportunity to come to know the Comforter. There is no other way to know His strength than to run into the end of mine.
However, because He allows us to endure challenges and trials, we experience the essence of who God is. He is loving, patient, compassionate, kind, sensitive to our hurt, and protective over us as His children. Finding comfort in God in the midst of suffering turns despair into hope. Pain into solace. Anger into peace. It makes us into the kind of people God wants us to be - more like His Son.
Furthermore, if my eternal destination is to be in Heaven with Him, shouldn't I want to be there? Shouldn't that "reward" be something desirable to me? In fact, if this promise of Heaven is what God says it is, shouldn't it be the greatest thing I could ever imagine (great enough to make the suffering worth it)? Shouldn't He be the fulfillment of my every hope and desire?