Well, one much debated theory suggest: 10,000 hours! We need 10,000 hours of ‘deliberate practice’ to master a skill and become expert in it. Popularly it’s called ‘10,000 Hour Rule’ (Do we really have 10,000 hours to master a single skill?). We (freely) advise not to trust this rule as we think it’s rediculous and new research support us that suggest such deliberate practice makes a difference of just 12% in your perormance. So, don’t get afraid by this rule as it may not be a rule at all!