Almost everybody has one or two things that they find hard to get in their diet. If you’re vegan it might be B12 or iron. If you live in the North it might be vitamin D. If you're a denizen of the Western world, omega 3 is a likely candidate. Whatever it is, it can be hard remember to take it daily. Fortunately, there’s an easy way to remember them: put them in a pillbox with a different compartment for each day of the week. It lowers the barrier of getting vitamins, especially if you take more than one per day, and it makes you feel more psychologically motivated by seeing yourself work through the week instead of an endless bottle.
If you want to really make it motivating, add a jelly bean or a vitamin you like the taste of (vitamin C and calcium often taste good). As always, if you want to make something a habit, try to make it intrinsically enjoyable.
I'm an effective altruist who co-founded Nonlinear, Charity Entrepreneurship, and Charity Science Health (Suvita)