This post is more so a running inner dialogue as I have not completely figured out how to successfully throttle my efforts to achieve maximum output without ever reaching the burn-out phase.
When you first start at a job, everything is exciting and you're able to work your ass off to get near the point where you can contribute at a level your accustomed to. As you start to catch on and get familiar with your new job, it takes less effort to achieve what you need to as the amount of unknown barriers and new technologies to learn begin to dissipate. I do not believe, however, that your work ethic and output have a direct x = y correlation.
If x is work ethic and y is the output, I believe there is a coefficient that needs to be calculated into the equation. This coefficient is how smart you work, which for this example we will call z. In my mind, the real equation is x * z = y where z is a number between 0 and 1. If you're working as smart as you can, z = 1. If you're meandering your way through your work, the value of z drops to some arbitrary number less than 1 (i.e. .65) and your output drops even though your work ethic remains constant. Working unintelligently can be as simple as falling off the critical path on a project by not focusing on the crucial parts of a project and putting too much energy on the trivial parts.
In my experience, burning-out typically causes your z coefficient to drop and in result causes your y value to drop as well. When this starts to happen on a regular basis, you enter into the burn-out phase.
The burn-out phase I'm referring to is when work needs to be done, but your completely apathetic to actually making it happen. Another symptom is when you become surly when discussing a project and demonstrating reluctancy to change the project for the better as it would result in re-engineering some of your initial efforts. I plan on addressing some remedies I've used to get through these periods, but first you have to identify what type of burn-out phase you're going through.
There are two types of burning-out that I believe exist. One is a short-term problem and the other is much more serious long-term problem. The short-term problem I see is typically when you have worked really hard or long on one project and it simply keeps getting larger or every time you think you've crossed the finish line somebody tacks on an additional 10%. The 10% can be scope creep or it can also be bugs that you originally lacked the foresight to test for. Either way, I consider this type of burning-out a short-term problem. Here are some ways to avoid or break through the short term burn-outs:
Grinding it Out
I know what you're thinking: this is a shitty remedy. Sorry, but for a lot of the barriers you come across, grinding it out will resolve the issue. Sometimes you just need to suck it up and crush it. If you find yourself having to grind it out very often, then there's probably a bigger underlying issue and you'll need to find a more sustainable solution then just adding more to your workload.
Getting your Little Wins
It's the little things in life. You can argue otherwise, but the smallest things can often have the most profound changes in your mood and outlook on life (or work). You need to identify where these little wins are and get them. It's important to keep things in perspective as well. The average developer makes $75k a year. That means your company is dropping $1,500 a week on you to do your job. If you take off one day from being lazy or burnt-out, you essentially just wasted $300 of your company's money. If you were to take that $300 and do something with it to remedy the reason why you're taking a day off, then you're doing yourself a solid as well as the company.
It doesn't have to be big either. If your little win is getting a bigger monitor, new computer or new coffee maker and you think this will make you happier to the point where you'll be productive, I guarantee it will pay for itself a couple times over. It doesn't have to be physical goods either. If getting to the gym during the middle of the day gives you more energy and revives your second half of the day, then do it. If your boss asks you why you need what you're requesting and you explain to him/her that it will make you more productive and relieve the stress of your monotonous day, there's no reason for him to say no (assuming he/she is rational). It's almost implied, but I'll say it anyways - every time you ask for more, more will be expected of you so be careful not to overdo-it.
Disconnect for your Sanity
If the two suggestions I wrote above don't work, get out of town. Take a little vacation to anywhere that will make you seem disconnected for your work. First, actually leaving your work and not allowing yourself to come into the office on Saturday or Sunday will force you to work more efficiently during the week as your normally flexible working window is now confined by outside forces. Once you're out of town and you've worked hard to take care of everything that needs tending to, remove the tether to the electronic world. Turn-off emails on your phone and don't open your computer. Engage in conversation outside of your profession. If you're a developer or work at a start-up, avoid talking about the tech. like the plague. Let your brain turn off and you'll free very refreshed and ready to go come Monday morning.
Abandon Routine for Perspective
If all else fails, change it up. Take your schedule and flip it on its head. Breaking routine will force you to take a fresh look on everything and re-evaluate why you do everything the way you do.
What if it's not a short-term issue?
The long-term problem is when either your job or the company you work for is becoming the common denominator for lack of ambition or motivation. I have only come across the short-term version of burning out and hope to never come across the long-term kind so I don't have any suggestions to counter-act this. The only thing I can say is that whenever you need to radically change a prevalent aspect of your daily life, you need to shake up your routine in a drastic way. Coming from someone who was overweight for a large portion of their life and lost 60 pounds 5 years ago and haven't put a pound back on, you need to do something big. Small changes are easier to relapse on and you'll fall back into your problematic lifestyle before you know it. You need to go down to your core and summon as much will-power as possible to generate some sort of movement against the current that has led you to your unhappiness your currently experiencing.