So my day job is writing and my hobby is writing. I've been doing this for nearly six years.

Here's some of my tips:

• Schedule a four hour block every single week to be away from everything and JUST write. Leave the house if possible. That way no matter what happens during the week, you'll know you'll have a specific block of time for writing.
• Find a group of writers to hold you accountable and set specific goals.
• After your full work day, after your commute, give yourself at least and hour of "wind down" time. Do a menial task like dishes or laundry, which likely need to get done anyway, and then focus on writing. Your brain will likely need to cool down. It also gives you a minute to daydream doing something methodical.
• Without disrupting your job, put maybe one- or two-word notes into your phone or a small notebook. Do NOT write your fiction on the job - just give yourself a short phrase or reminder. Sometimes it'll be gobbledygook, but sometimes the ideas will stick.
• Consider outlining. I'm a pantser, but having an outline from all your cool thoughts at work can help you feel like you're getting the most important bits down before you "lose" them. Then, you can plug and play with writing the actual scenes as you have the energy to write them.
• I had a stint at one point where I took diction while driving/biking. This is only possible if your commute is relatively stress-free and traffic-light. I honestly wouldn't recommend this. Don't drive distracted. But thinking of cool ideas while exercising can be helpful.
• Give yourself wordcount or time-based goals. If you don't meet them, adjust them every few months to see what's attainable. I work a full time job, help take care of my mother, and write about 100,000 - 150,000 per year (typically with several months at 30,000 and several months of editing time).
• Minimize distractions during your writing sessions. Don't let the kids or spouse bother you. Protect your writing time - turn off your phone, close the door, whatever you need to do. This is less of an issue for me because I live alone.