I trained three times a day because my body can't handle doing one 3 hour session. When I started really going heavy, I was going through a heartbreak and wanted to throw my efforts into something other than wallowing in self-misery. I kept it up even after I pulled out of it. Never let a good heartbreak go to waste.
My routine evolved slowly over time. The key is spotting and removing barriers to doing more. I put my jacket on the machine on the left, my towel goes on the right. My iPhone goes in the cup holder, my gym bag just under the cup holder. My gym bag has an organization scheme, everything in there has a place and there's a routine for putting everything there before I get in my car.
Basically, every little thing I can look at and try to improve, I do, and don't worry about the time or expense. I've gone through three pairs of sneakers to try to find the right kind that won't hurt the balls of my feet. Cheap ones don't work well, so I'm moving on to New Balance. I had minimalist shoes, those hurt my feet, but not enough to where I can't work out. The shoes have to be 8 1/2 or 9 wide, normal doesn't cut it.
My music routine has shifted over time. I used to just play anything, then I went to a specific playlist so I could try HIIT. Whenever the chorus would come on, I'd go really hard. That got unsustainable as my times on the machine went up and now I just do it flat, with my whole playlist so I don't get bored of the music. Maybe in six months to a year I'll be able to experiment with it again.
The machine itself has settings, my approach to these have refined over time as well. I used to set the incline all the way to 20 and slowly increase the resistance over time. Now I set both the incline and the resistance as I'm comfortable and just trust that over time my body will adjust and the numbers will go up.
The key to getting started, I think, is to pick something that can be "routine-ized". I use a machine instead of running because I have a lot more 'knobs' to tweak. Classes I have to take on someone else's schedule, I used to do dance classes but not anymore. I tried the bike machine when I first started going to the gym but gravitated to the Arc machine pretty quickly and fell in love with it.
At first the big battle will be just showing up. I started with the simple goal of going there once every day. Didn't matter if I actually worked out or not, or what I did, just get to the gym that day and I gave myself permission to feel like I'm accomplishing my fitness goals.
Then when it starts getting hard, I gave myself permission to fall back to earlier goals as needed / desired. I can cut workouts short, but not skip them. I always make sure I'm moving forward.
There finally comes a point where moving forward is moving backward. You don't want working out to overtake the rest of your life. But you have to cut back with purpose, not just do it because of reasons. You can put it on the back burner, but know why you're doing that and when you're ready to put it back on the front burner.
I'm injured right now, so I'm allowing other things to take priority. They may keep priority even after I heal up. But getting back in the saddle and getting back to work pushing my limits is always on my mind.