Some thoughts that have helped me in my life so far:
Do not bottle your feelings up. Do not hold back your worries and concerns. When things get really bad, you'll be more prone to meltdowns and will in all likelihood find it even more difficult to convey your feelings in a calm manner that won't totally freak other people out. Besides, if you talk about your feelings more often, you'll get more practice doing it, and will become more comfortable with it. Make sure that you're pro-active in resolving issues in your life immediately, before they worsen into something unmanageable.
Let the people you care about and trust see you break down. If you don't have people in your life whom you trust, do it in front of a mirror instead if necessary. Maybe you don't want them (or yourself) to see you break down because you want to show them that you are strong. However, it takes an even stronger person to admit one's own weaknesses, limitations, and failures. And the strongest person of all will take those admissions, learn from them, and build onto what the person does have, and become an incredibly strong and mature adult as a result. Don't ever be embarrassed about your problems. Having problems simply means you are human, and nothing less than that. It also means that you aren't just taking the easy way out in life, and that in itself earns my respect, not to mention that of many others who know and understand just how difficult it truly is to be a self-supporting, independent adult in this world. There is no shame in facing and tackling your fears and limits head on. So keep your head help up high!
Accept that sometimes you might not have the ability to solve a problem at that particular moment. You can do everything perfectly right, and still have a problem happen, and it won't have anything to do with you personally. Sometimes we're victims of circumstance, or knowledge and experience. Rather than banging our heads on the wall, thinking about the problem endlessly, and becoming despondent, sometimes it's best to put the problem aside, and tell ourselves, "ok I'm not in a position to deal with this right now," and do our best to put the problem aside. Move on, continuing to meet new people (hopefully some of whom you will be able to trust and open up to) and do new things, learning and growing. After some time has passed, and we've accumulated more knowledge and experience, we can then perhaps revisit this problem that once plagued us, and find it then much more tractable. Time and distance help to provide us with the perspective needed to see things more clearly, equipping us with more effective means of dealing with our problems and weaknesses. That way we won't lose sight of all the great and awesome things in life we can still enjoy.
_________________
Won't you help a poor little puppy?