Experience.
Firstly, 10 fluency units per day is fast enough (we mean 10 fluency units per day NET not gross). Fast enough to blast through a whole GCSE curriculum in less than a year. Fast enough to blast through an ‘A’ level curriculum in less than a year (assuming you already completed the GCSE before you start). And fast enough to complete a degree course in half the time given. So 10 is fast, 10 per day is an EXCELLENT performance – make no mistake about it.
Leaving behind exam courses, 10 per day is fast enough to go from zero to B1 level in less than one year and B1 is the level around which most people become happy that they can have fun with the language in the way they imagined when they started. And most people feel that one year is a reasonable time to spend acquiring a language they can use for the rest of their life.
You could do 20 a day. We have, we have clients who have. A young man who needed to reach B1 in Portuguese in 3 months (about 30 per day), a young lady learning French who just finds her rate of progress at 20 per day to be exhilarating and fun. And it is exhilarating and it is fun – but for most adults with busy work schedules, it is difficult to maintain, difficult to fit around their many responsibilities and priorities – so it is only a suitable goal in certain specific situations.
You could do 100 per day if you develop your skills and get some coaching support. You could take a month off, the right month in your life and blast through to B1 in that month. Why not?
But in our experience, what is a less good idea is going more slowly than 10 per day. Of course, there are circumstances where that is appropriate. The danger is that the rate of progress becomes insufficient to maintain enthusiasm and enthusiasm is what you need to keep going and to stay focussed. 5 per day is possible, it can sometimes be appropriate, but it is dangerous. Perhaps this is why students at school and university struggle so much with their motivation.
So raise your accelerated learning skills to where you can comfortable learn 10 fluency units per day in 10-15 minutes and then try your best to stick to 10 per day through thick and thin – good times and bad. The year will go by pretty quickly.
[Lot’s of people are learning 10 fluency units per day GROSS, some “A” level students do, most university students do. Some learn maybe 20 words once or twice a week, that does not make 10 per day on average but they feel they are learning that fast. But the absolute key is your NET rate of progress. It doesn’t matter is you learn 100 fluency units per day if you forget 95. In fact, I’ve met university students doing almost exactly that except it was 50 gross per day and 5 per day net so they were only forgetting 45 units per day or, put differently, 9 tenths of all their time was being wasted. It’s odd, we live in a world where educators especially are always talking about the importance of self-esteem then wasting 90% of a student’s time. Don’t they realise that wasting people’s time is the ultimate insult and that that insult repeated endlessly for many years will do more to damage self-esteem than most other forms of insult?]