Karmanyeb adhikarste ma phaleshu kadachana

Here is the 47th shloka from chapter 2 of Gita.

Karmanyev Adhikaraste Ma Phaleshu Kadachana,
Ma Karmaphala Heturbhur Ma Te sangostva Akarmani

The list of word meanings are taken from this link.

karmaaNi = in prescribed duties
eva = certainly
adhikaaraH = right
te = of you
maa = never
phaleshhu = in the fruits
kadaachana = at any time
maa = never
karmaphala = in the result of the work
hetuH = cause
bhuuH = become
maa = never
te = of you
saN^gaH = attachment
astu = there should be
akarmaNi = in not doing prescribed duties.

In a more laymen english, it roughly translates to ...

You have every right to action i.e. you have right to do your duties.
However, you do not have any right on the outcome. i.e. for example if you have been good and honest in your life, do not assume that you are entitled to a good life.
Keeping in mind the fact that action and consequences are separate entities, do your duties without keeping the end in mind. Never falter from your duty, be it because of fear or be it because of your want for something bigger / better.

Do what you know is right. Do what you feel is right. Do what your conscience says to be true. Do not be tempted away from the right path. Do not be afraid to follow the right path. You only have right to do, to action. The outcome is already decided and executed by God. You do not have any control on that.

If you are interested in knowing more about Gita, click here, or click here.
If you want to read this shloka in Sanskrit and a more authentic translation, click here.