"When in doubt, don't. Consider the task and ask." If you're not sure you're going to really be able to help somebody, you might interfere with them, then don't do much. You should ask them first, or ask somebody else their opinion. The middle ground is accepting the fact that: "Well, I'm not sure".
If we are sure we can help, then fine, we go ahead, we offer our help, try to do something. If we are certain that it's not going to help then fine, we just back off, and we don't do anything. But that "middle ground" is the area where we're not so sure. Maybe we could help, maybe not, but since we're not so sure, it can be helpful to talk to somebody about it. Best is to check with the person you want to help, if it is appropriate. Do they want assistance? Are they open to you offer of help? If you can't talk with them directly, then try to talk to somebody else to see what they think.
We certainly don't want to go about helping people in a way that it does interfere with what they're doing, because that's not always helping anybody, is it?