This question has two solutions.
The first is at the level of character — you need to break the habit of being careless and sloppy.
This requires long-term practice and conscious, deliberate attention on your part.
You need to carry this mindfulness into everyday life as well — be careful and precise in all things.
Many people have a misconception: they think being careful and attentive at work is enough, and wonder why they need to be so diligent in ordinary daily life.
But in reality, your brain needs constant training to maintain sharp, attentive habits — so pay attention even in the small moments.
The second is a simpler, faster method.
Take the things you need to consider in your regular work and turn them into a template.
For example, when you write a proposal, what factors do you need to account for?
Organize and summarize them — list them out: 1, 2, 3, 4, 5.
That way, the next time you write a proposal, you can think through your template point by point, and nothing that needs to be covered will be missed.
The template may not be fully comprehensive at first, but as you work, you can gradually enrich it — and eventually it will cover every detail without exception.
Working from the template every time is also highly efficient.