God's assurances and promises are for believers to appropriate. These promises are like precious gemz that needs to be discovered through diligent search. The challenge, however, is we're either too lazy, too unmindful or too distracted and preoccupied with the things that life designed to keep the gemz from us, so we'd not maximise their benefits.
Isaiah mentions one of such assurances, "Fear not [there is nothing to fear], for I am with you; do not look around you in terror and be dismayed, for I am your God. I will strengthen and harden you to difficulties, yes, I will help you; yes, I will hold you up and retain you with My [victorious] right hand of rightness and justice" (Isa 41:10 AMPC). This is similar to the assurances God gave Paul in Acts 18: 10: "For I am with thee, and no man shall set on thee to hurt thee: for I have much people in this city."
When God makes you an assurance, it is meant to inspire full confidence in Him, where you're persuaded without doubt to trust him. In these uncertain times, what can you do and how far can you go without trusting in God. Trust him when you can or can't figure out your next line of action, do not rely on your own understanding. Do you know nothing shakes or moves those that trust in the Lord (Psa. 125: 1)?