If you feel no more power to drive, better to change.
If you spray or make interior or exterior nicer, at the end no power or comfort to drive, you won’t have mood to drive..

I just sold 13years old 1st gen Myvi... have done lot of interior/exterior customisations and only use it for 2 years then sold off. At the end still not happy/satisfied.

I suggest go for new Myvi or 2nd vios or altis or city