I tried things like this for 5 years without success. I'm not convinced that an external tool or person can enforce a behavior. If you want to be more productive, I recommend trying what I've been doing for a few months; it seems to be working great. Here's my full daily routine:

First, I don't turn on my computer until I've finished my morning routine (wake up, read a book, eat breakfast, shower, go for a walk). I find I'm less prone to distraction when I'm fully awake.

When I do turn on my computer, the first thing that comes up is my to-do list. It's sorted by priority, and tasks are written so that each can be started right away. There's no decision about what to start; it's the topmost item every time. The reason this is so good is it makes it incredibly easy to get started (and on the highest priority task too!)

I've found that using my computer at night interferes somewhat with my biological clock, so I use a program to remind me to start my bedtime routine. After the reminder goes off, I brush my teeth, put on my pajamas then either watch videos or read for a bit to wind down before going to sleep.

tl;dr: Blocking access to reddit probably won't help. Instead, make it super easy to identify and start your most productive task.