Modern martial arts classes cater for a wide variety of student:

1. Sport
2. Fighting
3. Young children
4. Performance art
5. Preservation classes
6. Self defence courses
7. The gym approach (drop-in and work out)
8. 'Feel good' groups that focus upon the emotional and psychological benefit

There is arguably something for everybody.
However, many of these classes have nothing to do with the purpose of martial arts training.
The modern student can train what they like, how they like.
The important thing is to be honest with yourself concerning the nature of what you are practicing.

Once upon a time martial arts were taught for very simple, pragmatic reasons:

1. Personal protection

2. Professional combat skill

Nowadays, things have changed.
People are often too lazy to learn how to protect themselves.
They imagine that a cocky 'attitude' and a big mouth will work against a real life assailant.

The need for professional combat skills remains the unchanged.
Guns and batons may be widely used by security/military services, but robbed of their weapon, an individual still needs unarmed combat skills.

Bai shi is all about integrity and trust.

Is the student capable of furthering the art?

Are they true to the art?

Can you leave it in their hands?

Do they inspire your confidence?

Students of the Tao must appreciate one thing:

Every day, mindful practice.

When the mind is disciplined

then the Way can work for us.

Otherwise, all we do is talk of Tao;

everything is just words;

and the world will know us as its

one great fool.

(Loy Ching-Yuen)

Doing the right thing at the right time is all a matter of reading the situation correctly, and responding appropriately.
Initially, it is quite difficult. With practice it becomes easier.

Learning to follow and exploit the line of incoming force is paramount.

If you make the wrong movement, you will find yourself locked into a contest of strength.
Remedy it by using the three dimensions. 
A person cannot have strength in all three directions simultaneously.
Change and you will find their weakness.