It's never too late to start and it's never too soon to quit

[Glen]

For "It's never too late to start and it's never too soon to quit" I just made up

Nunca es tarde para comenzar, tampoco temprano para abandonar

but would like to hear any better way to say it. It's a good thing to say.

[poli]

It sounds OK. Maybe you can say no existe un tiempo inoportuno para aprender
ni para abandoner sus estudios.--- or something like that.

[AngelicaDeAlquezar]

I propose "...ni demasiado tarde pronto para renunciar".
"Temprano" is normally used for "early" when talking about hours of the day, and "abandonar" needs the complement "¿abandonar qué?"

[aleCcowaN]

Nunca es tarde para empezar ni pronto para abandonar.

[Glen]

Thanks to both. I can use both suggestions. Hey aleC, just out of curiosity why empezar instead of comenzar?

[aleCcowaN]

Regional and personal preference. To me empezar is more related with having a beginning and comenzar more related with beginning, though are almost interchangeable:

La función (de cine, de teatro) comienza a las 9 y termina a las 11.

Nunca dejes sin acabar/terminar lo que empezaste.