This is a huge and highly personalized subject but I would like to provide a bit of direction that I have learned along the way. From this and other questions you have posted it would appear that you are looking into a career in the Dental field. I would first suggest reaching out to your current dentist to see if they would allow you to do a job shadow to observe the actual job being performed. This could be hugely beneficial for you. From a broader standpoint, I would suggest the following:
1. Understand who it is that you want to become. I don't mean from a professional standpoint but as a human being. What kind of person do you want to become. Who do you aspire to be? When you have a clear vision of what type of person you want to be and work toward it, most other considerations become far easier. This is because you can look at each decision and quickly determine what choice will bring you closer or drive you further from becoming the person you want to be. This may seem incredibly basic, and in a way it is, yet too many people really have no idea who they are becoming or why.
2. Prioritize. Learn the difference between actual needs and wants and then operate accordingly. Life has the obnoxious tendency to test your priorities. If we don't prioritize or (even know) what the most important things are to us than we will end up with far too many regrets. There will always be more to do than we will eve accomplish and no one on their death bed ever wished they had spent more time in the office - time is a limited resource so prioritize and use it wisely.
3. Control. In life there are only a few things you can actually control. Everything else falls into one of two buckets - things you can influence and things you cannot influence or influence in any significant way. Spend the majority of you energy on those things you can actually control. For example, you can control how you think about yourself, on the other hand you can only influence how others may think about you. Spending excessive time fretting over what someone else may think is counter productive - its out of your hands anyway. Similarly, screaming at the television when your favorite sports team is losing may be fun but does not actually influence the outcome of the game.
4. Forgive. You will make mistakes. When you do, work to resolve them and forgive yourself. Making changes and moving forward is often the best thing you can do in a bad situation. Wallowing in regrets and self pity will never serve us well. Pain is part of life, take time to mourn if needed and then move forward. Similarly, there will be some who will wrong you. They may already have. Don't allow the bad choices of others to burden you - holding grudges or resentment is unnecessary baggage. On the other hand don't allow yourself to continue being hurt by others either. Some people are simply not good to have in our lives. Don't be too hard on yourself or others, we are all in this together!
Best of luck to you!
I am assuming you want to be a dentist or related field. I am not sure the extent of your question, and expectations but let me give you some personal advices I also got along the way:
1. Understand what this field is all about. There is more than just the dentist that clean or fix your teeth. There is an entire industry behind it, from equipment manufacturers to the industry that make the consumable products. There is also various types of dentists. I would ask my local dentist, orthodontics, other dentist in the area what is their job about. Also possibly check online for the industries that provide them with their equipment.
2. As an adult, you may want to build a family of your own. Think about it. A job that requires a lot of your time means that it will leave you with less time to spend with your friend, family (close and extended). Think about this. The more time you have to spend at work the less time you have for the rest.
3. You do not prepare your future in a day. Find internships, experience various positions as much as you can. I knew a dentist who, at 30, was totally tired to see mouths. If that something you get disgusted about no matter what, think about a dental position when you are away from people. Maybe same if you do not feel nice around people you do not know, because you will have to be with your patients.
4. Force/push yourself a little: there are many people who will tell you do only what you like or love. Sometimes, it takes more than one try to start appreciate something. Do not stop at the first failure to like it. Try it differently, try it again. If really you cannot stand it, drop it but do not do it at first feeling.
5. Learn: from your mistakes. Because you will make mistakes. The goal is to learn from them. But in order to make mistake, you need to do something. Do not give up on that mistake, grow from it by first pardoning yourself and then understand what you can do better to not reproduce it again. Talk with more experience people.
I think you took the right first step by asking here. Maybe ask a more precise question to start with so you may get more answers.
I hope that helped.
Consider the resources at the student doctor network (google it).