Observing vratas is part and parcel of Sanatana Dharma.
Vratas are restraints.
Restraint over physical and mental tendencies.
You feel hungry, the natural tendency is to look for food.
Then you put a restraint on this, it becomes a vrata called upavasa or fasting.
You feel like sleeping in the night, this is natural, but then you keep awake and listen to divine stories, this is a vrata.
When you are with people who are familiar to you, you feel like talking to them,but if you observe silence it becomes a vrata, mauna-vrata.
So vratas are essentially restraints.
One such vrata is Karva chauth, very popular in North India.
It is observed on Krishna-paksha chaturthi in the lunar month of Karthik.
This is particularly for sowbhagya, long married life , health and longevity for the husband.

Observing a vrata is optional. It is voluntary.
Nobody compels you.
If you decide to observe a vrata, do it properly.
Don't do half heartedly and don't make compromises.
Follow the exact procedure.
There is an interesting story related to Karva chauth.

There was a princess called Veeravati. She had seven brothers who were very loving and caring.
Veeravati was married, her brothers were also married.
Once, Veeravati and her sisters-in-law were observing Karva chauth.
When you do that vrata you are supposed to be fasting till the time the moon rises.
At moonrise, you offer arghya to the Moon and then only take food.
Veeravati got hunger pangs at sunset, she was unable to bear it but somehow carried along.
Seeing this, the brothers got very worried.
They arranged to make a big fire beyond the mountains to make it look like moonrise and told their sister: Look, the moon has risen, now you can take food.
When Veeravati sat down to take food, the first morsel when she took, she sneezed.
The second morsel, there was hair in it.
Bad omens.
As she took the third morsel, news came that her husband died.
Crying, she went running towards where her husband was.
On the way, Lord Shiva and Devi Parvathy stopped her.
They told her that it was because she violated the rules of the vrata that this happened.
But they knew that she did not do it intentionally.
Veeravati repented.
Devi gave her divine water and told her to sprinkle it over the body of her husband.
He came back alive.
Simple story.
But shows the importance of sticking to the rules of the vrata.
Even an unintentional violation, look at the consequence, her husband died.

Do these vratas only after you fully understand the significance, the norms and the rules.
Vratas can give you tremendous power.
But at the same time, if you don't do them properly they can be counter productive as well.