Lately, I have seen a lot of people that have no belief that they are capable of doing anything they set out to accomplish.
While I know there is no easy solution to convincing ourselves we can, I suggest you just flow with the opportunities that come along. If it feels right, do it, if it doesn't then just let it go and wait for something else to come along. But don't give up completely and look for excuses as to why you can't do something about it. Keep yourself in control of what you choose to do, this includes your own happiness. You can only control your destiny so stop worrying about everyone else's! Be your own inspiration and while you learn to inspire yourself and push yourself forward to achieving whatever you desire, be a positive driving force to those around you. Be an influence for someone else to make the changes.