"Be thou my strong habitation, whereunto I may continually resort: thou hast given commandment to save me; for thou art my rock and my fortress. Deliver me, O my God, out of the hand of the wicked, out of the hand of the unrighteous and cruel man. For thou art my hope, O Lord God: thou art my trust from my youth. By thee have I been holden up from the womb: thou art he that took me out of my mother's bowels: my praise shall be continually of thee."
What happens when your phone batteries die and you run out of cartridges for your gun? Maybe it's your money or your ability to reason? Riches make themselves wings and fly away. Is it your charm and personality? All these fade away with time, or else are gone in a moment. All these fail and change, but God never changes. He is the only sure thing on which you can trust.
You may be trusting in Jesus to get you to heaven, but you think you must find your own way or make one while on earth. But no! You can trust God to see you through your life also. Are you trusting in your job to put food on the table? Or maybe the government? Or are you trusting in God?
Just think of Abraham. What would it be like if it were you? You're 75 years old. God tells you to leave, but he doesn't tell you exactly where to go. Abraham trusted that God knew where he was going, so he set out. He had no cellphone to call for directions or to make reservations. He trusted in God to keep him from dying of thirst, starving to death, or dying of diseases. I don't suppose there were truck stops every few hours where they could get water bottles, shade, or medical aid. He couldn't have loaded up into a truck and gone back when things got too tough. He traveled in an area where he knew no one. Bandits could have snuck up on him, killed him, and taken all his stuff, and no one would have known.
Abraham trusted God. Sometimes it may be hard to know what you're trusting in until it is no longer there. When you pull out of your driveway onto those dangerous roads, are you depending on your ability to avoid all possible dangers, or blind luck that you'll not be one of the many killed every day in car accidents? Or are you committing your life to God's care? He can do much better than we humans.
If you are totally and completely dependent on God while everything is going well for you, you will still be able to depend on Him when everything goes wrong. You'll not be afraid of losing your strength or becoming old because you never trusted in your youth or strength.
"Hearken unto me, house of Jacob, and all the remnant of the house of Israel, which are borne by me from the belly, which are carried from the womb: And even to your old age I am he; and even to your hoar hairs will I carry you: I have made, and I will bear; even I will carry and will deliver you."