I don't think basic self-care is a matter of deserving or not, it's what keeps you alive. If you don't eat or drink well, things will only be much worse than they are already, mentally and physically, so why not?
Perhaps buying food and drinks you really like might also convince you to grab them more often? Just don't go
too unhealthy.
I also have some other "convincing" arguments that are helpful to
me, but from an ethical point of view I should probably not share them. I suppose one can guess them. ^^