When listening to a band, your impression comes from the combined performances of the players. However, when playing in a band, or just with one or two friends, it is tempting to listen to your instrument only. Clearly it is better to have the same perspective of the band as your audience, i.e. to hear the whole sound and not just your own. Better harmonica listening skills will help develop this perspective and will improve your playing.
Most of will have seen bands where one player seems not to fit in. While this "odd player out" may be technically skilled, the chances are that they are focused on their sound only, and are not listening to the other players. This is a bad habit, particularly for a harmonica player. Here I’ll suggest some strategies to avoid this.
When first playing with others, the experience can be overwhelming. In my early days as a player, I used to stomp my foot so vigorously that little else could be heard. Over time however, your solos and fills will start to gain attention and approval from your musical peers and audiences. Once you are comfortable with your playing, then try this mental exercise.
Imagine that you are at a mixing desk, with a separate fader (volume control) for each player in your band. Now turn down your own volume. What you are doing is hearing less of your sound, and more of the other players. This can be hard at first. Then, while you are playing, try to focus on an individual player, for example the bass. Identify their riffs, and absorb their tone. Then move on to another player, for example the guitar. Move around the entire band, while continuing your solo (or rhythm part). Then focus on the collective sound of the band, with you just a part of it.
This exercise is difficult, but very worthwhile. In particular, it will help you better appreciate the people you are playing with.
The next step is to grasp what the band is trying to achieve. Then, try to determine how your part will further this goal. It could be that a given song needs just a simple solo from you, which restates the melody, with nothing else during the verses. This may require you to leave some of your tricks "in the bag". It is far better to do this than to overplay, and spoil the overall band sound.
A final point is this. You and your band will sound much better if the rhythm is solid. When you take solos, try to lock your ears on to the bass notes, or better still, the drums (assuming they exist). By doing this, even a simple solo can sound great, and more importantly, lift the whole band.