Concerns over going from 1.5 lbs a week to .5

I've got 20 lbs left to lose or so. I'm seeing a lot of people on here saying that for that amount of weight to lose .5 lbs a week is ideal. I started out on the 2 lb a week plan and realized that was a bit aggressive backed off to 1.5 now. Thats about 1590 calories a day. There are plenty of days where at the end of the day I'm eating a snack, or having a beer just because I haven't reached my goal for the day, not necessarily because I'm hungry, and plenty of days where if i work out i'm under calories. Ideally i try to average 1900 calories or so and burn 300 on the stationary bike (using HRM). I'm concerned about slowing down to .5 a week that I'll be eating way more than feel like and working out even less, and end up losing motivation. If this is working for me can i stick to it, or do i really need to slow it down?