Use "learn of" in situations where news or new information is received. Use "learn about" to refer to studying, investigating, or becoming familiar with a subject.
Use "learn to" to express that someone is acquiring a new skill or behavior. Use "learn how to" to emphasize the process or method by which one acquires the skill or knowledge.
The phrase "short-term pain for long-term gain" is often used to express the idea that immediate sacrifices or difficulties may be necessary to achieve greater benefits in the future.