Having a good relationship with your colleagues can make for a much more pleasant working environment. You may even go so far as to call those colleagues your friends. But regardless of the level of trust you've established, there are certain pieces of information you should never share with the people you work with. Here are a few in particular to keep to yourself.

1. Your salary

Discussing compensation at work might seem like a good way to see if you're being paid fairly, but in reality, it's a move that can backfire. First of all, your company might actually have a policy that prohibits employees from discussing salary information (or at least frown heavily upon it). Violate that rule, and your good standing at work could get compromised.

Professionally dressed women chatting in an office setting.

IMAGE SOURCE: GETTY IMAGES.

Additionally, talking salary at work might cause resentment if it turns out you're being paid better than your colleagues. If others grow bitter, it could wreck your relationships and create a situation where people are less willing to help you out because they feel you're being given special treatment. And of course, things could work the opposite way, too -- you might come to resent your co-workers if it turns out they're earning more. If you want to know whether you're being compensated adequately, a smarter bet is to use sites like Glassdoor, which provide salary data by industry and geographic location.

2. That you're looking for a new job

These days, it's common for employees to jump ship, and moving to another company could be the best way to snag a raise or promotion. But until you're staring at an offer letter, you're best off keeping the fact that you're searching under wraps, at least as far as your co-workers are concerned. You never know when an otherwise earnest or trustworthy colleague might accidentally blab, and if it gets out that you're looking, and your manager doesn't react well to that news, you could find yourself demoted or even out of a job.

3. Gossip about other co-workers

When you come upon juicy information about your colleagues and their personal lives, it can be all too tempting to share those details with an interested associate. But don't do it. If the subject of that gossip finds out you're overstepping your bounds, it could damage your relationship and make working together extremely unpleasant. Worse yet, that person might report you to HR. Furthermore, the last thing you want is to be known as the office gossip, so if you really feel the need to dish out details on somebody else's life, find an outside friend to talk to.

4. Your personal financial situation

Perhaps you're struggling to cover your bills. Or maybe you come from a wealthy family or have a spouse who does very well. No matter your circumstances, sharing personal money matters is something that can turn an otherwise strong relationship into an awkward one.

Consider the former scenario. If you let on that you're not doing well financially, you might get judged as irresponsible. Or you might make others feel uncomfortable to the point where it affects your daily interactions. Then there's the flipside. If you let on that you're well off, and your manager finds out, he or she might use that as an excuse not to give you a raise. Similarly, if your company can only offer a handful of salary boosts in a given year, you might get passed over by virtue of your strong financial standing, when the decision should actually be based on merit alone.

5. That you sometimes play hooky

Many of us have limited vacation days, so if your company gives sick time its own separate or limitless tally, you may be tempted to feign illness to snag some extra time off. And if you're smart about doing so, you can probably get away with it fairly easily. But if you make the mistake of letting your co-workers in on your secret, it could come back to haunt you.

First of all, you never know who might share your tactics with your manager or HR, and if that happens, you risk a series of consequences, the least of which is not getting paid for the days you pretended to be sick. Second, if you call out sick during a busy period of work when you're not actually ill, your colleagues might come to feel abandoned or put off when they're forced to absorb your share of the workload. You're better off squeezing out some extra leisure time on the sly, and keeping it to yourself.

It's one thing to be friendly with your co-workers, but there's also such a thing as being too open. Steer clear of these dangerous topics, and your relationship with your colleagues will be stronger for it.