Negotiating price but not buying same day

In Canada, and this would be my first car (22F).

Going into a Kia dealership later this week to test drive a 2021 Kia Rio with 30k km on it. Currently it's listed at $18.3k CAD with a $250 incentive offered by the dealer for used cars. Not certified pre-owned, just used.

My mom is telling me to go in for the test drive, negotiate a price down, leave and make a decision, and come back in a few days if I really want the car to do paperwork etc. I'm inexperienced with negotiating car deals, and this dealership I'm visiting is quite far away from me (around 1 hour driving, I'm renting a car to go to this dealership for this car). I feel conflicted about if this is the correct approach, as I feel like I'm potentially losing negotiation power by leaving and then coming back asking for the negotiated price a few days later, as well as me having to make potentially three trips to the dealer for the test drive, paper signing, and picking up the car.

I've been searching for a car for a bit, and this one looked really promising, which is why I'm willing to travel a bit to check it out. In my mind, if I can get it for 19-19.5k out the door I'd be willing to pay for it on the spot. Not sure if this mentality would make me weaker for the negotiation process though.

I would appreciate any advice on how to approach this situation. TIA!