I had not one, or two, but three conversations tonight with various people who are scared of life's uncertainties. In every case, the feelings are rooted in the notion that what they say or do isn't of any value. (Related: Fear, change and risk.)
Let me make something very clear up front... I'm not particularly happy right now with some aspects of my life, and my self-esteem is not at a high point. So when I offer advice like this or make observations, it's not out of some superiority complex, I just think I'm better able to keep some level of perspective.
Everyone has different reasons for doubting themselves or dismissing the value of their thoughts and feelings. There are the basic things like, "What will people think?" or, "What do I know?" Then there are the more deeply rooted things that come from parental influence, romantic relationships, and to a lesser degree, shitty job situations. When those external influences build up over time, a person gets to this ugly place they actually believe the bullshit that has been imposed upon them, that they really don't have anything meaningful to contribute or feel.
It's hard work getting around that. I was lucky enough to have an awesome therapist who bypassed the "how does that make you feel" nonsense and got to the meat of the "you need to start believing in the value of your feelings." It takes practice, and at every corner, you need to catch yourself feeling bad or scared or whatever, and realize:
"These are my feelings, and they are real and legitimate. No other person, or society, can take these feelings away or invalidate them."
Once you have that realization, and stick to it, you need to do the harder thing and start getting the people out of your life who violate that premise. They exist as lovers, bosses, friends and sometimes just overall environments. It's never easy, but it's quite liberating to be out of those kinds of toxic relationships.