Many of us hear the negative insecurities and fears of others being projected towards us through the "you can't", or "that won't work" statements of negativity. These statements are rooted in these peoples own fears and insecurities. They are afraid of failure themselves, so they try to discourage you too. Don't listen to this advice from others. In fact, distance yourself from these people and find people who encourage you.
"Whether you think you can or you can't, you're right." - Henry Ford
In the pursuit of happiness, it is extremely important to follow your dreams, passions and find your own path to achieve the life you're after. Surround yourself with as many people that are positive towards your goals, and distance yourself from those who are constantly trying to bring you down.
This negativity that others try to push onto you is something that I refer to as "Poison." You need to eliminate the poison from your life. Just as poison kills the body, it also kills the mind.
If you want something, all you need to do is simply take a single step each day towards the end goal. There is no such thing as overnight success. All success is the culmination of tiny steps taken repeatedly over a long period of time. Just like climbing a mountain, the path to success is taken a single step at a time.
Find your passion and work to take a single step towards your goal every day. Follow your own path, and break away from the crowd that's perpetually poisoned by negative people.
You can succeed. You can reach your dreams. You just need to be willing to do what it takes to get there. Never give up, and remember to keep taking it one step at a time.