(This is borrowed from “Chabadtalk.com,”  a forum on which topics in Chabad are discussed in personal terms. I’ve written previously on the Tzemach Tzedek’s ‘Think good and it will be good.’  The post below expands on it admirably. It can teach us a lot about practicing faith, whether as hitbodedut/personal prayer or as a sincere, heartfelt attitude.)
“…The non-Chassidic understanding of bitachon is that it means trusting that Hashem is in charge of everything, nothing happens if He does not will it to happen. In this view, Hashem is not beholden to you by virtue of your trust.
In the Chassidic view of bitachon, if a person trusts that Hashem will provide him with parnasa or health or whatever it is, Hashem will respond with that which the person seeks.
Here’s a practical application: In the non-Chassidic view, if a person is seriously sick ch’v, it would be wrong for someone to tell him, ‘Tracht gut, vet zein gut” (‘Think positively and it will work out well’), because who knows? Maybe Hashem has other things in mind? Maybe that’s false hope in a bleak situation?
I have heard this view expressed time and again among non-Chassidim.
The origin of ‘Tracht gut vet zein gut’ goes back to a story of a chassid of the Tzemach Tzedek [the third Chabad Rebbe] who went to the Tzemach Tzedek because his son was on the verge of death. The Tzemach Tzedek told him, ‘Tract gut vet zein gut,’ and the child recovered. When did the child take a turn for the better? The moment the chassid began thinking this way.
The Rebbe emphasized this greatly.
Some ask, ‘Who says a person deserves whatever it is that he’s praying for? Maybe he won’t get it because he’s not deserving’?
The answer is: BY VIRTUE OF THE TRUST, the person gets what he prays for, EVEN IF he’s not particularly deserving. If a person goes beyond his limitation, and trusts in Hashem in situations where doctors tell him it’s hopeless, or just the situation itself seems hopeless, Hashem responds in kind.
My favorite story is about the talmidim of the Besht who were sent by the Besht to a man to learn about bitachon. As they visit with him, a man comes in and pounds on the table and then leaves. Their host explains that this is the first warning from the poritz that he must pay the rent. He seemed relaxed about it, and when the man came in a second and a third time and banged on the table, he still seemed calm. The talmidim said: ‘So you have the money?’ and to their surprise he said he didn’t.
The talmidim watched in great curiosity as the man set off to the poritz’s mansion to pay the rent, with no money in his pocket. They wondered how it would play out.
In the distance they saw a wagon approaching the host, stopping, and then traveling on, then stopping again, turning around and going back to their host. Then their host continued on to the mansion.
When he returned, the talmidim were eager to hear what had happened. ‘So, did you pay the rent?!’
‘Of course,’ he said.
‘How did you do that if you had no money?’ they wondered.
He explained that the farmer in the wagon that approached him had offered to buy the produce that would eventually grow on his land. He made an offer but the amount was not enough to pay his rent, and so he DECLINED. That’s why the wagon drove on.
But then the farmer changed his mind and drove back [and said,] ‘I know you to be an honest person, and if that’s what you think you should get, I’ll pay you.’ And the farmer gave him the full amount, whereupon the man could pay his rent!
A modern-day version. I heard this from a cousin… A few years ago, a…daughter became dangerously ill in a reaction to some medication. She was at death’s door, and when the father was at the Ohel and somebody suggested to the father ‘Tract gut vet zein gut,’ he figured he had no other choice. He decided that if he was truly thinking positively, he would prepare a seudas hoda’a [“meal of thanks”] for his daughter’s recovery. He actually called the caterer etc. and yes, his daughter made it to the seudas hoda’a! 
Some people don’t understand this and say: ‘But I did think positively and yet it didn’t ‘work’.’ The answer is, these words aren’t a [chant] to repeat over and over. In the story of paying the rent for example, the host’s entire being was one of utter trust that Hashem would enable him to be able to pay the rent. It’s a mindset, not a prayer or segula [good-luck charm or amulet].”
This is also what Rabbi Lichtenstein teaches about “affirmative” and/or “visualized” prayer: See only the state in which you desire to be; affirm that you are already in that state. The Divine Mind responds in kind.
In the above story, the father’s “affirmation” is expressed by his preparing the meal-of-thanks before the healing has even taken place. It is as if to say, “In my mind, she’s already fully healed.”
The author distinguishes this from a verbal expression in prayer, saying that merely thinking positively casually doesn’t produce the desired result. Similarly, the late Doris Friedman, from whom I learned the basics of Visualization, told me that Mrs. Lichtenstein had taught her that a visualization should be so real that if, for example, you see yourself sitting on a summer beach, you should actually begin to perspire!
At the same time, we must always remember that by our affirmation or positive thought, we are not creating the outcome ourselves. We’re allowing it!
Rather like floating on water: the more we struggle to stay afloat, the less we actually keep our heads above water. When we learn to lie back, relax, and allow the water to keep us up, we float effortlessly.
Positive thoughts, trust or prayer are the same: The more we struggle with doubt, fear or anger, the less the Divine creates the outcome we desire. Our own will is in the way. The more we allow the Divine to act — by affirming that the action has already taken place — the more of an outcome we’re promised.
In this regard, I’ve sometimes found repeating a positive statement for a prolonged period can help lead to the desired state of mind.
So, “repetition” can be a tool, and emunah/faith can be a “skill” that we develop gradually.
“Faith forged and practiced throughout life seems to be that soft place on which to rest when tragedy comes our way.” 
 i.e. the father prepared to thank G-d for his daughter’s complete recovery, while she was still direly ill and not expected to recover.
 Harris RN, Trudy; Glimpses of Heaven; p. 137