People can be depended on to act consistently...
Consistency is a good quality to have in your personal behavior, particularly if it is acting consistently decent with your interactions with other people. Communication and interacting well with other people is an art and requires a certain effort and being true to your own self. Consistency though doesn't mean always acting the same and that everyone acts well consistently.
We all have moments when we act in ways that we wish we didn't. I can think of a recent incident where I was scathingly rude to someone who consistently never follows up or does what he is asked to do. My actions were uncalled for however but even more so, a waste of time and negative energy. Why? Because I know that he is consistently lazy and will never do the job he is paid to do in any reasonable sense of timeliness or completeness.
When I was thinking about this later, reasoning why I flared up at him when I know he's never going to do anything he's supposed to do on time or completely, I recognized that both of us were acting consistently in our own behavior. Also I realized that acting consistently doesn't always mean acting consistently good but can also mean acting consistently bad.
In my case anyone who knows and works with me knows that generally I am usually calm and even-handed, if anything some people consider me too calm since I rarely get frantic over problems, because in my mind that does no good. What they also know is likewise I can be counted on when someone repeatedly does the same thing over and over again that irritates me, no matter how much I've tried to correct the situation, if they continue to do it, I'll finally lose it. It's never pretty or done lightly either when I do.
"God deliver you from a man with a very long patience, when he finally loses it."
In this instance I think most people would say that I consistently act as a decent guy who does what he says he's going to do. The person I was dealing with consistently acts as if every day at work is an inconvenience and his actions at work reflect his entire character, at or away from work, and he can be counted on to not care about doing anything fully or well. It's irrelevant to me his personal life is a wreck due to it, I just expect him to be inconsistent with his character at work and do everything correctly, which I've finally concluded is unrealistic.
The key is that people can be depended on to act consistently the same, whether it's reliably or unreliably. People are pretty persistent in their character and actions. There are always exceptions to their behavior, for example my habit of losing my patience after a long period, although I'm generally considered very patient. Occasionally that lazy person just actually may do some things energetically and on time.