The building of Saint Peter's Basilica was a far longer and more complex project than the modern observer tends to appreciate. It took two centuries, and the reigns of thirty popes, from Nicholas V to Alexander VII, to complete. There were many intrigues along the way, many ups and downs; it was an epic filled with disasters, failures, terribly mixed motives, and also great examples of genius and true art. If it could be said of ancient Imperial Rome, Roma die uno non aedificata est, then Renaissance Rome, with Saint Peter's as its crowning glory, was likewise much more than an overnight phenomenon. From the point of view of the middle of the project it looked for a long time like a hopeless endeavor, one that had no apparent end on the horizon. In fact, the very phrase la fabbrica di San Pietro took on the idiomatic meaning of a project that has no end in sight.
My point, besides the fact that I think this is interesting history in itself, is that I think the building of Saint Peter's is analogous in many ways to life in general. God knows what is planned for your life, and for mine. He knows what will be accomplished, what will be the final result. He sees the beauty and genius of it from His perspective. We see the raw material; He knows that in and through it all He is bringing about something great.
The Lord rarely calls us to see our own success. He does call us to see with the eyes of faith that He is succeeding at doing His will in our life, and to trust that it all works together for good, a truly great good. He has our life in His gracious and almighty hand, and sees that what He has done is good. He beholds it, and sees that it is very good. For we are called according to His purpose.
All manner of sin was involved in the building of Saint Peter's, and yet that is only a type of the great sinfulness of our own lives. Out of the building of Saint Peter's came a work of monumental beauty; how much more so is the beauty of one human life in Christ.
I encourage you to consider your own struggles in this light.