One of my favourite phrases is 'Don't give up the day job' for when someone is not very good at something. I put together 'Noli labor a die dedere'. However 'labor' is more 'task' instead of 'job' and would like a better alternative for 'by day'. Could anyone give me a better translation?
An adjective for “day …” or “daily” would be diurnus. But you are being a bit too literal. It is a peculiarity of English that a person's regular occupation is called their “day job.” I think negotium fits the bill.
Likewise, dedere is not a good fit either, it means “surrender, yield,” etc.
So I would suggest:
Keep the day job.
or less terse:
Interim retine tuum negotium.
For the time being, keep your day job.