Feather has some good initial thoughts. Tied in with that, I have one tip on what NOT to rely on:
Anger, fear, and frustration. People who struggle with executive function (as in, doing something on time) spend so long pressing this button long after it’s ceased functioning for a very good reason: It USED to work! It SOMETIMES works! It’s the technique How to ADHD calls “Hulk Smashing through the Wall of Awful”.
Hoooowever. As well as the downsides How to ADHD mentions (that it damages your relationships and self-esteem), building up enough adrenaline to get something done is extremely costly to your body--when you invoke the body’s stress response, you’re diverting a lot of resources from normal healthy processing--and it gets less useful the more you use it. Your body loses its sensitivity to that level of stress and you need ever-increasing amounts of anger and fear and frustration and self-hatred to motivate yourself. If you use this method enough, you can eventually become completely desensitized to these emotions, and literally no amount of them will motivate you, and it can take months or years of low-stress living before your brain will begin to respond to them again.
I hit that point somewhere around year four of a 2-year Master’s degree program. It was Not Fun. (I just had a dream last night that I had to go back to Vancouver to finish an assignment I’d left undone or they’d take away my license to practice. I graduated half a decade ago.)
So one thing that works for me is to think in terms of what we know about optimal productive experience, a concept in psychology called Flow:
Flow means hitting the sweet spot of something challenging and interesting enough that you want to do it, and that you feel you have the skills and ability to do.
So if you want to be able to do something, you need to adjust the parameters of that task to make it either easier, more challenging, more interesting, or less overwhelming, until you feel capable of doing it.
For people locked up in the realm of anxiety, that often means cutting your workload until it actually feels manageable--lowering your standards or decreasing the amount you’re expected to take on until you can start. Often once you’ve started, you feel more capable and can up the challenge level again, but it can be important to give yourself an on-ramp.
On the other hand, it may involve increasing the skills you bring to bear. You can cast around for any related skills, anything that it feels like you do easily or well, to help you out, or even just remind yourself that you’ve been skilled enough in the past to help your confidence.
If what you’re dealing with instead is apathy or boredom, then you may need to make something more of a challenge or more intrinsically interesting, until you have a reason to want to do it. This is why gamification of basic tasks, like Habitica, can be so successful.
Other than that... I have an executive dysfunction tag, How to ADHD has a video on overcoming the wall of awful, and ADDitude mag has a whole ton of stuff!
