I am a teenage Muslimah who is a big worrier. If mom goes to take my sister to Arabic school I worry that she will get in an accident or some such thing. I try to calm myself because it puts me in a lot of stress, yet since the year before, when I tried to do that and my mom had gotten in a car accident, I became increasingly worried. What do you suggest that I do and is it even good to worry so much?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

We pray to Allah to grant you success to do good deeds and to protect you from every evil.
Our sister! Know that Allah, as stated in the prophetic Hadith narrated by Imam Muslim , has preordained all matters fifty thousand years before the creation of earth and Heavens, so why to be afraid or worried!
Thus, you have to be pleased with the Qadr (Divine destiny) so as to attain Allah's pleasure.
In this vein, the Prophet (Sallallahu Alaihi wa Sallam) said: "The more distress the more reward; if Allah loves some people, He tries them. So, whoever is pleased (with such distress) Allah will grant, him pleasure; who ever becomes dissatisfied, Allah will be discontented with him" [ al-Tirmizi ].
Another Hadith reads: "Be satisfied with Allah's Qadr (Divine Acts, grants), then you will be the richest and the most satisfied one among people" [ al-Tirmizi ].
Belief in al-Qadr is one of fundamentals of Iman (Faith); one's Iman is still incomplete unless one believes in al-Qadr. Appointed times of death and portions of livelihood are in the Hands of Allah, i.e. no one can change their time or quantity. So if such a state becomes well established in a believer's mind, then he/she will live with bliss and assurance.
We advise you to be engaged in acquiring useful knowledge, in worship and Zikr of Allah, such as reading Qur'an and so on.
In addition, do your best to avoid obsessions and false impressions. After that, put your trust in Allah and pray to Him to guide you to what is best and right, since He is the Most Merciful.
Allah knows best.