When does it become too personal?

Whilst attending school, I never had good relationships with my teachers, it wasn't as if I hated them, I was just one who didn't believe that teachers and students should have a conversation based on more than the school content being taught.
I am in varsity, and am next year will be my final year, although I know my lecturers, its in the form of needing to understand why I received such a mark, or for the purpose that I was sick and would like to book an appointment in which I can find out what I missed. It frightens me to when I witness students who go out of their way to create a relationship with their lecturers, where they email them on a constant basis, where they feel the need to have a conversation with them before and after every lecture. I myself have needed to ask a question but I also feel I need to use some common sense.

It worries me, when I become a teacher in the next couple years, do I need to formulate those types of relationships?(I am not speaking about relationships of the intimate type) I do believe that its vital to learn about my students, to formulate a connection with them, and I believe that its vital for me to show my students some "human" qualities about myself, as the students then see me in a different light, my question I am posing is, when does it become too personal?

In South Africa, classroom sizes  range from 16 to 45 students, it all depends on the type of school. How does one teacher create a personal relationship with each individual student? I very much want to be that teacher where a student can come to me with any sort of problem, even though I myself never felt I could do that with any of my teachers.

It wont be easy, and I will constantly ask myself the above questions, so that I may become the type of teacher that has a connection with all my students, but will keep in mind that I am after all their teacher, not their friend, not their confidant, but rather, someone who will enrich their minds, will spark their creativity and love for English, whether it be poetry, or literature or even the idea of creating a piece of writing where they are able to get lost in their imaginations.

That will be my goal.