When I didn't fully grasp the truth that I am God's beloved it was hard for me to believe other promises that God had for me. It was hard for me to identify or reconcile little sinful me with a sinless Savior. God had to do a work in my heart for me to fully comprehend this. Maybe you need to reconcile this truth as well. Oh the freedom that domes when you fully understand it!
Resting in God then becomes second nature and we come under God's protecting shield and in the revelation that you are His beloved. Having that security in God and the knowledge of how he perceives you protects you from the thoughts and lies of the enemy that tries to tell you different. Meditate on this scripture and ask God for yourself how he sees you... and rest secure in His word!
Let the beloved of the Lord rest secure in him, for he shields him all day long.