Have you ever felt rather useless and unnecessary?  George Bailey did and more; he felt that people would be better off if he was never born.  But all he needed was a change of perspective.  I think those feeling (useless and unnecessary) are harbingers of change needing to happen.  We don't need Clarence and a Christmas miracle to get it either.  When we feel that way if we just look at what it is we do want and refocus our energy as to how to feel the essence of that want we can gain a new perspective.  
If you want to feel needed look at the people you surround yourself with, are there others out there who may need your help but you don't know them, aren't connected to them, or feel like you don't know how to help?  A girl at work recently was telling me how much she influences and guides her one friend, but that friend never seems to change.  We often want to help people because it is important to us not to them.  One of the biggest ways to help is to just be a great person.  You don't need to rescue someone from a burning car, a great example goes a long way and will be remembered when it is needed.  
You can't force anyone to accept your help, they have to ask, they have to connect with you, and you have to be able to leave the change and the work to them.
There are other ways to get change, to get back on track with a new perspective, but it is so individual.  I've often moved or changed jobs.  But usually it isn't about that at all, it is about inner work.  Finding the feeling essence of that change.  Do you want joy? love? freedom? passion? knowledge? support? peace?  Whatever that essence is, look at how it already appears in your life and support that.  I saw a meme recently that said: make a list of what you do, make a list of what you LIKE to do, adjust accordingly!  
Adjust accordingly, it's a wonderful life if you look from different perspectives and follow your essence.