As you start out on your career journey, there is no telling where you will end up, even with all the planning in the world! I want to encourage you to re-think the words that you use when having these thoughts. Don't think about careers "failing" or having a "back-up career." Think of it in terms of developing "transferable job skills" and "cross-marketable majors." It sounds a lot more positive, because it is!
No major will "guarantee" you a job in the workplace. I have worked with clients who should easily be able to obtain jobs, but they can't. Why? Because they lack one required component of the job description, or, worse, because of their personality - they are not a pleasure to be around. For example, if someone wants to be an Air Force pilot, a position which has certain height requirements due to the size of the aircraft cockpit, and they don't fall within the parameters, they won't get the job.
You like being around people, but are afraid of picking a low-paying major. It is not the major that determines your pay - it is the job! So, if you major in psychology/sociology, AND go into social work, you might not be happy with the pay. However, you don't have to go into social work. There are all sorts of jobs out there that want a degree - ANY degree, and, they pay rather well. You could have a career in banking or sales (such as selling funeral plans, or doing business to business sales, etc.)
Many people change jobs every 2-5 years, creating their own career progression as they go. In fact, some employers consider workers who stay with one job too long to be "stagnant," staying in their comfort zones because they are afraid to take chances. When you decide to apply to a different type of job than the one you had before, you will work on your resume, re-wording it to put emphasis on those skills acquired in the previous jobs that pertain to the one you are applying for. It's not nearly as difficult as it sounds!
My favorite example has to do with a customer whose experience was in fast food, but she wanted to work at a doggy day care facility. The job duties were going to involve a lot of cleaning. So, since she worked the overnight shift, she was accustomed to doing heavy cleaning, and that was what she emphasized.
Once you start working, keep your resume current, and stay alert for other opportunities. You don't want to be a job-hopper, but, at the same time, if a real good opportunity comes along, you will want to consider it.
A factor that definitely contributes to success in the workplace is what is called "Emotional Intelligence." It has to do with knowing how to navigate interactions with others, being sensitive to their feelings, and the ability to make them feel good about themselves when they are around you. If you are not familiar with this, I would encourage you to do some research on it.
I think it is great that you are researching these concerns now! Let me know if I can be of further help.