Music is organising Time
Music is organisation of sound in time and from that perspective our practise should be organising time also, since all practising is or should be really preparing for performance.
Even if you are on your own, you have to be performing with yourselves as listener. If you do that you can enjoy every minute of it, if - of course - you do more than practising the right notes.
Once you transcend the individual notes to catch the rhythm, the mood and the feel of a piece of music you are well on your way. For so many students practising a piece of music means playing it from the beginning until the end over and over again until the muscular memory of the fingers is trained enough so they will find their way through the piece.
And then suddenly when the situation changes, a different piano than at home or a lesson situation with a teacher or a small performance situation, suddenly the piece falls flat, because the subconscious memory has given way to uncertainty.
Your practise should therefor always be practising music. As soon as you have grasped the 'right' notes of the first two bars for instance, you should try to understand the meaning of the first phrase and practise carefully the first two bars. You have to create in your body the elements required to co-ordinate the movements of both hands and catch the mood of the phrase. That is fun, as soon as realise you are actually playing the first phrase. It makes all the difference like between letters and words or sentences!
More over once you have grasped the phrase structure of a piece of music you will realise it is not that long after all. In the beginning many attractive pieces of music go from 16 to 32 bars at the most, so there is nothing against it to master the first 4-8 bars only of a piece of music in the first week.
The guitarist John Williams said once that typically he would never practise more than one hour a day. But he was very grateful for his father to have taught him to practise very slowly and intelligently, so he would never practise mistakes.
And once you have mastered to play 4 phrases of a piece, knowing and understanding every aspect of them, it is not so hard to play these phrases in a new performance situation with confidence, for instance your next music lesson...