Deliberate practice is practice that is typically guided by a coach that has specific goals, involves continuous stretching of the body and mind and, by nature, is hard.
If you have felt the challenge when learning a new skill [whether it is a tennis swing or the guitar] from a coach, you have tasted deliberate practice.
And, behind every great prodigy such as a Mozart or a Tiger Woods, there was typically a coach [in their case, dad] who developed their skills early.
These practice techniques have been refined over time to the delight of competitive parents globally.
Search for “child prodigy” on YouTube and you will notice the increase in the number of child prodigies over the years.
Often, kids with innate talent, be it IQ’s in mental tasks or better physical attributes in physical tasks, may get a head start. But, it does not count for much without deliberate practice.