Yud Bais Tammuz 

This was the day the Frierdikker Rebbe was miraculously granted freedom from the murderously cruel Russia under Stalin yemach shemo. He took this as a sign to exponentially increase and intensify Chabad's efforts to create and support Judaism in all fields and to all Jews. 

Some beautiful and meaningful thoughts from the Frierdikker Rebbe:
Obviously Chassidus ALWAYS focuses on the positive. Unfortunately sometimes rebuking another is necessary. In such a circumstance one needs to be very careful when administering rebuke.
In his letters he stipulates the mindset and precautions when there is a need to rebuke another. 
He draws an analogy from an operation. Before the doctor cuts and goes in to heal, he administers anesthesia, for without a painkiller,  a successful operation is impossible.
Before rebuking/cutting into another and trying to make that person better, make sure you administer a "pain killer", make sure that the person you will be rebuking won't feel pain, for it is impossible to help another by causing that person pain. 

In another letter he uses the analogy of a doctor that administers an injection to a patient. The doctor first needs to sterilize his hands and his clothes, he also needs to sterilize the area where he will be administering the injection. Why does he need to go through all these precautions? Because if bacteria of any type gets into the patient's body, the patient will be far worse off after an inconsiderate and careless treatment. 
If rebuke is necessary, first wash your own hands and clothes and make sure you yourself don't have any negative issues, for they are like bacteria and are infectious. If you didn't take care of your own issues first you'll end up making the rebuked person far worse off with your inconsiderate careless intervention. 

From another letter,
Medicines in general are either poisonous or extremely unhealthy substances. Only administered in extreme times, in exact doses and by a qualified individual can this negative substance help. 
The same applies with rebuke, it is poison and only in extreme times, in exact doses by a QUALIFIED individual will the rebuke have a positive outcome, otherwise the opposite will occur.

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The Frierdikker Rebbe's whole life was about overcoming challenges. Here is his insight into understanding the purpose of challenges: 

In all aspects of Mitzvos, the main focus is in elevating something. For example, leather - as in making Teffilin and a Sefer Torah. Food - by making a bracha we are attaching a higher calling to this food to give us the strength and energy to live a Jewish life. Work - elevating the money one achieved, by giving to charity, paying for Jewish education, supporting a family. 

Different are Nisyonos/challenges - tests. The purpose of a test is only for the one being tested - to overcome it mentally and emotionally. The single purpose of a nisayon is to elevate ONESELF, to stay positively focused on doing good. The F"R quotes his grandfather (the Rebbe Mahrash) - Regarding a Chossid that due to his livelihood, needed to be around extremely low morale characters and very compromising situations, yet the Chossid stayed strong and unwavering in his thoughts, speech and actions. The Rebbe Maharash, seeing how great a person this Chossid had become due to his withstanding any challenges to his Chassidishe