I get nervous with very small little things. In this case how could I overcome my nervousness?

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

As for the reasons of being too nervous and the ways of overcoming this, they are as follows:
A: One should think about the consequences of nervousness. If he does so, he will become patient and forbearing.
B: One should learn about the good turns of patience and forbearance. The Prophet Muhammad (Blessings and peace of Allah be upon him) said to Ashaj Abd Al-Qays: "You have two qualities that Allah and His Prophet Muhammad (Blessings and peace of Allah be upon him) like: Forbearance and patience". [Muslim].
Allah Says while describing some people that he likes: (Those who spend [in Allâh's Cause - deeds of charity, alms, etc.] in prosperity and in adversity, who repress anger, and who pardon men; verily, Allâh loves Al-Muhsinûn (the good­doers).[3:134].
C : Know also that the brave is the one who could control himself when becoming angry. The Prophet Muhammad (Blessings and peace of Allah be upon him) said: " The strong one is not he who knocks out his adversary, the strong one is he who keeps control over his temper". [Bukhari & Muslim].
Allah knows best.