When do you know how to let a project go?

Hey. I've been trying to get an automated newsletter off the ground (premotely.com). I tested the market with a basic landing page (£10 total cost for the domain). Since then about 150+ people signed up off of one LinkedIn post and a few test ads on Facebook.

I was trying to use Integromat and MailerLite to automate the creation of a job listings newsletter. But i find now that everytime I sit down to chip away at it, my motivation evaporates pretty fast.

I have some encouraging early numbers; the first (manual) newsletter i sent out had a 59% open rate and 18% clicked on at least one job.

I keep butting up against one issue or another with MailerLite and Integromat. I know I should just get on with it and do a little every day. But one day I will think it's better to focus on something else. The next day I find myself thinking "its worth trying to grow this!".

How do you know when to cut it loose and when to keep going?