If we don`t judge emotions as "negative", and be mindful of emotions as they arise - we then see that, e.g. if there is this emotion of inferiority arising, we can cognize it, as being there. Mindfulness then "says": Oh, there is inferioirity because of this or that event. Or stress because of this or that. Friend picks up his cell phone when I speak my heart out, "this" and "that" is perceived. Then we could go and ask ourselves, why we react with these emotions to these events the way we do? Do we seek approval of others and feel bad/ less of worth if we don`t get it? Do we approve of ourselves enough? Do we get sucked in non-approval or can we just perceive it and let it be and instead approve of ourselves anyway? Etc.
If you feel stress (job, social events, something else), you could become aware of that and then ask yourself "why that is". What could be done? Work less, get a less stressful job? A more meaningful job? Become socially more relaxed as to make social situations stress you less? We should not believe (atleast I don`t), being mindful does all the trick. First we become mindful, and then we can act accordingly, if action is necessary to be taken - or refrain from action (e.g. hate is felt, but not blindly acted upon etc.). Sometimes the act of becoming aware of / mindful of does the trick, also, e.g. when feelings of inferiority arise and we do not indulge in them or identify as them being "me" or "mine".
In terms of inferiority, I notice it`s arising, and let it be, and let it pass. By indulging in it, or repressing them ("feeling them doesn`t help anyway) we`re ime not being helped. We are denying the very moment, which creates resistance to the fact you have feelings of inferiority triggered by certain events. It is so; I can`t give some scientific cause-effect-study that tells you why running from that is not particularily helpful and why accepting it without identifying with it as being "me" is helpful, other than my words :-P
The "right way to reduce it" would IMO be then, to become aware of, and then take correct actions / make the needed changes (if any are necessary). Ask yourself why you feel stressed, what is the cause of constant stress / feelings of inferiority, what steps could be done to change it etc. Your consent needs to be strong, to not let others determine your value / trigger a sense of inferiority in you, it is built, rather than just read in a quote and then applied as in "ah I understand - fixed." and done. Another quote could be "We cannot change who we are later if we don`t accept who we are now". Accepting all the range of emotions, thoughts and "issues", then, is the very first step, and mindfulness your companion all the long road down. Maybe in two years from now you will feel superior-issues, and you need be mindful of that and remind yourself of the sameness value all of you/us have and not live "that" out blindly, for example. :-P
If the hurt of not being the groomsmen stems from your own expectations, or the hurt of someone checking their phone of your current interpretation of that very situation (e.g. he`s checking the phone, he doesn`t listen, he doesn't care, I`m worthless bla), then feeling the feeling and cognizing it, maybe going into "why" you feel that way in the first line would most likely help you not feel that way the next time, because you don`t associate someone checking his phone while you tell him/her something something important with sense of worthlessness or not being appreciated by the other person. Or tell the other person that for you its a sign of disrespect, he may apologize because he didn`t know / it was not his intent to signalize that ... and if he then does it again intentionally and it hurts, you can take proper action. Feeling the hurt in any way doesn`t be bad, but can actually be a spring-board for resolution, proper action and growth...
Hope that helps somewhat