by Reb Nati at Mystical Paths
It is written "when a man wishes to draw closer to Hashem he is sent opposition to strengthen his resolve to serve".
When a man resolves to do a holy task, such as taking on a higher level of Torah and mitzvot, going to a holy Tzaddik, or moving to Eretz Yisroel, he is sent minneus (difficulties). We see an example of this in the story of Avraham as he went to offer Yitzchak, he was sent trials. (as discussed in Likutey Moharan 74)
The reward is coming, but getting through the difficulties is part of the task.
BS"D - בסיעתא דשמיא