I can totally relate to this. Having worked largely from home for the last decade, this is something I've had to battle a lot. Not being in an office, there's no-one else there to motivate me.
Here's what's worked for me:
10 under 10:
Every night I write out 10 (or more) tasks, each under 10 minutes. I make sure there's a few super easy ones (coupla minutes each) at the top of the list. That's what I work on the next day.
10 mins is a good length. It means you have to think down to near the deepest level of a task. I found with 20 min tasks, it's very easy to get mentally lazy, & next thing you know you're depressed/unmotivated coz something you thought would take 20 minutes is actually a day's work, full of subtle gotchyas.
Each day I try to do 10 of these tasks. If I achieve 10, I know I've had a good day. Thing is, once I've done a bunch of them, I'm usually motivated enough to do to a ton more. Eg, today I've done 79 (so far).
10 * 10=100 minutes of coding may not sound like a lot, but you'd be surprised how little actual work most people do (see: Office Space).
I keep two lists: the 10 under 10, and my 'done' list for the day. As I do something, I c&p it from the former to the latter. That way if I need perking up during the day, I can just look at my 'done' list to see how productive I've been.
Identifying limiting beliefs:
This is a bit trickier. It's easy to see the noise at the top level of our mind (mental chatter: "This problem is too tough for me" "I can't do this" etc). That stuff is relatively trivial to let go of (just decide to, you're the boss of your brain).
What's trickier is finding the subconscious stuff, doubts etc that affect our behaviour, but don't necessarily rise to the level of conscious thought. What I've found is that a lot of times things are so abhorrent that our mind "protects" us from them by hiding them. You can only see that you're being limited by looking at your output (behaviour, patterns, productivity etc).
A useful framework is this:
1) Assume you can do anything (as you pointed out, within this field there's no reason you can't).
2) From that basis, anything you're not doing is because you WON'T. Thus,
3) Ask yourself "Why won't I do X?" - with the followup question "What am I afraid of?"
What I've found is for every "won't", there's a fear behind it.
Now, the super subtle thing is this: You won't necessarily get any internal (mental) answers to these questions. However, if relaxed & attentive, you may feel tension or energy rising in your body in response. This is your body's physiological connection to those deep fears. Know how when you get stressed you tense your shoulders? Yeah, it's like that.
So, when you feel that energy or tension rising, in response to the questions, just let it go. Make the choice to consciously relax & let go of that tension. As you do, what you're doing is simultaneously letting go of the associated belief. Keep letting go till you feel relaxed about the questions.
Those two techniques combined have worked wonders for me, coming from exactly the same situation you describe. Good luck!