The Rebbe's teaching on what trust in G-d really is — and why it brings the good it trusts in:
"Think good and it will be good." Trust is not only accepting what G-d sends; it is confidence that He will do good, and that confidence itself draws the good down. Positive thinking brings positive outcomes (IK 665, 675, 2617, 3316, 6676, 7100, 7453). Avoid negative or gloomy thoughts even inwardly, since they can bring about what one fears (IK 1792).
Ask for the good, not for the strength to bear the bad. A request for mercy should not include a readiness to accept suffering; trust that G-d can help beyond natural limits (IK 1067).
No room for despair. Despair has no place in Jewish life (IK 6070). Even when things are hard, keep hope and a positive outlook, and blessing and improvement follow (IK 4039). Irrational doubts that undermine one's well-being come from the yetzer hara (IK 3872).
Delays are for the good. Delays and unexpected turns are guided from Above for our benefit, and everything comes at its proper time (IK 3316, 6866). Trust G-d as the true Healer (IK 6866, 10159).
Strengthen it. Recall past kindnesses with gratitude (IK 990, 3706). Elul and Tishrei are especially suited to strengthening trust through prayer, Torah study and tzedakah (IK 6491). Share your optimism and help others around you think positively too (IK 6676).
See also: Bitachon – Trusting G-d and doing your part; Bitachon – Worry, fear and anxiety.