I imagine if the oyster who is stuck with the grain of sand could express it's feelings, it wouldn't always be grateful. The oyster may even resent the pain that it has to go through at times. If you had a rock in your shoe all the time, it would get annoying after a while right? But the oyster doesn't give up. It keeps working through the pain, through the irritation. The oyster keeps fighting until one day, there's no longer a rough piece of sand inside them.
Or what about the tree that grows through the solid rock cliff. How much do you think that seed had to fight? Do you think it may have wanted to give up at times? If a tree could feel, I bet it would have moments of discouragement. Not every seed that drops in a miniscule crack grows. Only some grow, but it isn't easy. They have to withstand a variety of circumstances and trials. When they reach the point of breaking through, though, it's beautiful...a testament of perseverance through pain and suffering.
When this life gets to be too much we have to remind ourselves to look forward, we have to fight to keep going...to push through the pain. Because in the end there will be beauty that comes, whether we see it (or believe it) now or not. These days, it's hard to hold onto that truth...to believe it. I get tired of fighting like everyone else. But I have to hold on, to have hope in the Lord, because His promise is clear...
"Trust in the Lord, and do good; dwell in the land, and feed on His faithfulness. Delight yourself also in the Lord, and He shall give you the desires of your heart. Commit your way to the Lord, trust also in Him, and He shall bring it to pass." Psalm 37:3-5