I hear this so many times; I can't sing and won't sing because i sound awful and have been told I can't sing in tune. I often find that students who have difficulty singing on pitch tend to listen to their favourite song and then just go for it without any awareness of hearing themselves and how they actually sound. Compare this to a competent singer who has honed their craft from a very early age and has practiced mimiking their favourite artists, adjusting coordinations naturally and not being afraid to try different pitches voices and sounds.
Many people who feel they can't sing as adults have developed a fear and a lack of confidence from childhood. For example, being told to be quiet, or your not good enough to sing or join the school choir and as their personalities develop into adulthood so do the hangups and negativity that go with it.
For males often the problem occurs when their voice breaks. Before breaking the voice is very similar to a girls voice and can reach high girly sounding pitches. Once the voice breaks and often at first intermittently, boys tend to go in and out of both a deeper toned voice and their original higher voice and they find it very difficult to maintain control of their voice quality. This then affects confidence as none of us like to feel silly and boys especially tend to then fall in to the trap of talking in a limited range where their voice will stay in a low speaking range and that often is a very low lifeless mundane pitch to keep the voice from changing back to it's childlike quality.
Girls in their teenage years can have their own hormonal issues to deal with as they can go from being confident to feeling social pressures, awkwardness, emotional and self-consciousness among their peers and everyday life which again affects their confidence and voice quality to try things out of their comfort zone. For both males and females these issues can carry on through into adulthood which can ultimately result with a hangup to singing. The good news is with guidance these experiences can be overcome with good vocal training. Learning good technique can help you overcome your nerves and confidence issues to get to your singing goals. I'm not going to say it's easy! Like learning to play any musical instrument, it takes, time, patience and practice and there's no magic wand. But if you have the drive and determination you will get there.

