Background: I studied psychology and I have very close cases of AD(H)D.
Psychotherapy sometimes feels artificial since if what works would feel natural or obvious, well... we wouldn't need therapy, which is a handcrafted intervention (n=1). This is *really* important to remember while you are trying to improve/do therapy. More on this later [1].
A better mental model for reward-based interventions is to think about your inner "reptile brain" as a weighted graph that connects things (stimuli) with emotions and behaviors. Those connections are mostly learned throughout your life (and therefore "artificial"). And your brain is trying to find the happiest (and laziest) path in this graph.
A very motivated person tends to have a great graph that connects stimuli like "answering emails at 9:00 with music" to "happiness" or "hitting the gym" with "muscle soreness" and with "happiness with realization" and "tasting the morning coffee."
If your lazy, hedonistic, dopamine-maximizing brain does not have a path from the behaviors you want to create (e.g., answering emails) to something pleasant, it will be hard to make that a habit.
In a very explicit way, this sometimes looks like a point system. But don't think about the points. You have two very important tasks:
1. Find your "natural" rewards: coffee, watching TV shows, going for a walk, whatever you want to do, sex. And don't forget about internal rewards: self-respect, pride, nice words for yourself. Add to the mix social rewards: share your achievements... Each person is more sensitive to a different set of rewards. Find yours and pick the ones that make sense for your life context.
2. Make those rewards contingent on your goals. For example, I try to answer important emails first thing in the morning, especially those I want to avoid, and after that I go out for a small walk or have some tea.
Over time, you will internalize that conditioned (artificial) emotion for tasks that before felt horrible. Like many are able to feel nice when they have muscle soreness, because it was conditioned over time to something nice: social reward, internal/verbal rewards, techno music, whatever.
Don't forget to be nice to yourself, start simple with small goals, forgive yourself if you don't hit every goal at the beginning.
[1] Understanding this helps a lot in therapy or "self-intervention" because if you don't understand basic behavioral intervention and why it works, sometimes the intervention itself seems childish or stupid, and that hurts the efficacy. There is a huge body of research that shows that if the patient understands the therapy and has a mental model of it, it works like magic because we change from "I am doing stupid things because my therapist is saying them" to "I am nailing this, what a behavioral change I am making. That's great—in a few weeks I will be able to do X."