Something in your life isn’t going as you wish and you are feeling badly about that. In some circumstances, feeling badly can be helpful and productive. It’s about how you are doing your feeling bad: is it directed at the past or to the future?
Feeling remorse or regret is future- and change-oriented; it can spur on the change needed in your life. (This kind of feeling bad is called merirus in the Tanya.) It is thinking along the lines of “What can I do to correct the situation?” “What can I do (or not do) to ensure that this does not happen again?” Feeling remorse is helpful – but only in small doses and at appropriate times.
The other kind of feeling bad – wallowing in self-blame or self-pity or self-deprecation or depression – is past-oriented and not helpful in any way. It is along the lines of “I can’t believe I got myself into this mess.” “I’m such an idiot.” (This is atzvus.) These types of thoughts can lead to inertia and depression. There is no purpose in thinking in this way; the past is the past. It is worthwhile to learn healthy ways to jump out of such thinking.
When you are having negative thoughts, ask yourself: “Are these thoughts concerned with the past or with the future?” Don’t allow yourself to wallow in negative thoughts about the past.