Another very important component of having the proper mind set to succeed at online poker is courage. Now we can easily slip into going too far the other way and play carelessly or even recklessly, so we'll define courage for our purposes as having the resolve to act on what you honestly feel is the proper decision. Misuses of this will include not being brave enough, and also being too brave, so to speak.
What we're seeking here is to align your poker decision making with your actual play at the table, and ensuring that they correspond. We don't want to let fear cause us to pass up on what would be the correct decision, and on the other hand, we do want to refrain from acting too boldly when the reasons for not making the play outweigh the reasons for making it.
This applies of course not only into particular decisions at the table, but perhaps even more notably, it also extends into longer term considerations as well. For instance, you may have the proper skill to be profitable long term in a given scenario, but a bad run of cards may place you behind in the shorter run. Providing you indeed have the skill here, you also need the proper amount of courage to see things through and not allow the circumstances to take you off your chosen path. For instance, you may be considering altering your game by becoming more conservative, letting yourself pass up on what would be profitable opportunities overall by not wanting your bankroll to sink lower if you lose. You may have some valid concerns about managing variance if your bankroll becomes too thin for the particular game and level you're at, but what we're talking about here is being more motivated by fear than proper bankroll management.
In all cases though, what you need to focus on is long term expectations of value in given plays. If you're basing your decisions on this, and thus doing so correctly, you want to have a very good reason to deviate from the plan, and simply being fearful of your stack going down in the normal distribution of events doesn't qualify. The mistake that's often made here is that players tend to focus way too much on the situation at hand and not enough on the longer term. Asking yourself what the outcome would be if you made this move multiple times will help put you in touch with the proper perspective here.
With many players there will be times when you feel down or fearful or whatever, and you want to do everything you can do break yourself of this if you're going to avoid having these emotions cost you money at the table. Whenever this occurs, stop and ask yourself whether it's sound judgement that's prompting you to want to pull back here, or whether it's just being fearful of acting, or fearful of the outcome. Whenever you decide that it's sound judgement that's prohibiting you, then of course pulling back is going to be the right way to go, which could mean folding, betting less, raising less, just calling, checking, or whatever. If you decide it's fear that's inspiring your reluctance though, then you must act in the appropriate way anyway, even if this means forcing yourself to act.
If you often find yourself in these situations, by forcing yourself to act appropriately, over time you'll find that the instances where this is needed become less and less frequent, and eventually they will disappear, as you conquer these fears by simply acting against them. This is true generally, as well as at the poker table.
What you want to guard against though in acting contrary to these emotions is to overcompensate. Since your acting against these fears is an act of defiance of sorts, sometimes the action can become too defiant, erring on the other side of things. For example, say you are playing no limit and the action calls for a reasonably sized bet. Fear prompts you to bet less. You fight it though and it causes you to make too large a bet than would be advised, often pushing all in when you really shouldn't. These sort of overreactions can actually do more harm than good in a lot of instances. So what you want to do, when acting in defiance of your fears, is to stop and ask yourself if the extent of the move you're about to make in reaction to this is appropriate in degree or not. You both want to make sure it's sufficient and not over sufficient.
Perhaps even more often though is the case of the player who plays too boldly. Often these players hold boldness at the poker table in very high esteem, and want this style reflected in their actions, to too high a degree I might add. As good a trait as boldness is, when overdone it can be a player's undoing all by itself, regardless of how well he may handle other aspects of the game. Sure, there will be game situations where this overzealousness may serve the player well, and in that case taking advantage of these situations would be appropriate and not overbold. We're talking about a more careless style of play here though, acting without proper regard to one's profitability in fact. Being bold is a good thing, but we must see this as merely a means to a higher end, that being maximizing one's profits at the table, and not see it as an end in itself, as for instance what can happen when one fancies oneself as a very bold player and holds this as a higher ordered preference over trying to make as much money at the game as one can.
So to conclude, we must resist the temptation not to be bold enough at the table, and to be too bold as well, and this applies both to short and long term situations. Keep in mind that courage properly defined is a matter of executing properly, and there's a point where actions go from being courageous to just plain being foolish. Act courageously and not foolishly and you'll have very little to fear indeed.