"Have I not commanded you? Be strong and courageous. Do not be frightened, and do not be dismayed, for the Lord your God is with you wherever you go. This verse is awesome when I felt like giving this verse came to mind to pick me up again.
I struggle the most with trusting and faith. I'm very good at rationally working through things and saying, "Okay, these are all the reasons I can believe." But to trust when I am uncertain or don't fully understand yet, that's my deepest struggle.