My biggest hurdle is myself
I have had days where I sit and stare at a blank blender screen from dawn till dusk. I have had months without a single finished piece of art. I kick myself constantly for being unproductive, and that self-kicking only serves to make me less productive, it's a negative positive feedback loop. I'm sure this is the main reason why I am not currently soaring through the skies on a magic carpet made from the shredded prints of a million amazing artwork pieces I have produced.
But I haven't had a day like that for months now and it is all thanks to me. I have successfully trained myself out of inaction and underproductivity. Well, almost. It's a constant battle that will never quite be won. But here are a few strategies that make the battle a whole lot easier.
Have you ever spent a day staring at a blank screen with a blank mind
Only to spent the entire night in bed, wide awake, ideas racing through your head, muses dancing jovially on your cerebellum? Damn right you have or you wouldn't have read all this crap. Strategy number one is to emulate that night-borne ideas rush. Find a quiet relaxing spot to sit and just let your mind run over your craft. Two of the most effective locations I have found are in nature parks (no shit, trees just make me want to model) and bed. If you happen to fall asleep that's ok, you'll wake up refreshed. And don't worry about how much time you're wasting away from your project, it's just time you would waste staring at your blank screen.
Strategy number two is to start on something small. I am easily scared by big projects, so I do a fast mini project first. For instance today I was making totem pole models and I got a little overwhelmed. There was a lot of design decisions and loops and mesh repeat points and I started to slow down a bit too much for my liking. I decided to make some vine models I had been meaning to make instead. After a few hours I had the vine models finished and looking good, which gave me the motivation to model my totem poles. Or at least, do two different concepts.
Strategy three is not so much a strategy as it is a lifestyle shift. Sleep is way underrated. I know, most programmers/modelers/textureartistes/computerdudes love to stay up late, smash coffee, pull all nighters for no apparent reason, hard resets, crunch volleys and the rest of them. But it's not a good way to go. Eight hours sleep and a well nourished bloodstream does amazing things for my art. I can make decisions faster, comprehend poorly written shorthanded tutorials better, self analyze more effectively, it's just me2point0 with a proper sleep regime.
Those are the main pillars of motivation
That I have found helped me shake my habitual inactivity. But you don't have to stop there. Whenever you have a good session, think back on what triggered it. I know that playing Red Dead Redemption makes me get a hard on for blender within half a stroke so I also use that sometimes. If you find what makes you want to produce, make a mental note of it.
By far the most effective though, is the first one. If you are having real trouble creating, stop trying to create. Daydreams are like burley for muses.