"Some trust in chariots and some in horses, but we trust in the name of the Lord our God." Psalm 20:7
I think it's hard to discern in times of ease what we're really trusting in. Only in times of distress (verse 1) are the true hopes and habits of the heart revealed. However, it may be in the thoughts of the heart on a daily basis that one may obtain a clue. The thing we trust in counters the thoughts that creep in at some perceived or possible threat. It's obvious that there are two options for the foundation of trust: one can trust in the Lord, or one can trust in something else. The “something else” which supplants the Lord as a basis for confidence in distress is properly called an “idol,” and the trust itself is rightly called “idolatry.”
In verse 7, David discusses some potential idols - chariots and horses. In this case, the threat is military, and the counterbalancing trust is gained by watching the mighty strength of a finely bred horse pull the latest in iron chariot technology. The more horses and chariots, the less fear. David knew all about horses and chariots, and doubtless used them himself. But David disdained them as the true cause of a battle's outcome. As he says in Psalm 33:16-17,“No king is saved by the size of his army; no warrior escapes by his great strength. A horse is a vain hope for deliverance; despite all its great strength, it cannot save.” That's not to say that military ability is of no account, for David himself spoke of his prowess in protecting his father's sheep from lion and bear in his conversation with King Saul before fighting Goliath (cf. 1 Samuel 17:34ff). But even then, he gave final glory to God for his deliverance from those threats. God may use military skill and technology to accomplish his determined ends, but what matters most is the will and power of God in any trial.
What are modern equivalents of “horses and chariots?” Well, it depends on the specific threat or distress being faced. Threat: military; idol: stealth bombers, laser-guided “smart bombs,” etc. Threat: sickness; idol: medical skill, pharmaceutical research, modern equipment and techniques. Threat: joblessness; idol: personal/professional skills, lengthy resumes, “the strength of my hands” (Deut. 8:17), etc. Threat: poverty; idol: government programs. Threat: next week's exam; idol: my knowledge, studying habits, IQ, etc.
"Trust is a matter of the heart. And in times of distress or anxiety about the future, that in which we are trusting is revealed."
Now of course, as has already been said, God is a God of means. He even says “The man who doesn't work doesn't eat.” (2 Thess. 3:10) To rest lazily on God's intervention without using his supplied means is to cast oneself from the temple and put God to the test. If my child becomes seriously ill, I will not hesitate to go to a hospital. But trust is a matter of the heart. And in times of distress or anxiety about the future, that in which we are trusting is revealed. Proverbs 18:10 says, “The name of the Lord is a strong tower. The righteous run to it and are safe.” It's good for us to see that to which our hearts run in such times, and if it's an idol, to smash it down and replace it with a lively faith in the living God.