A present subjunctive that is the main verb of its sentence, with no ut, cum, si or the like governing it, gives an order or a wish: "let him …", "let us …", "you should …".
3rd person (jussive): "let him, let it, let them …": Ista tibi sufficiant "let these things be enough for you". 1st plural (hortatory): eamus "let us go".
2nd person: a milder command, "you should …", often best rendered as a plain imperative. Gataker uses it constantly for Marcus's advice to himself: contemnas, praestes, advertas.
The negative is ne: Ne te distrahant "do not let them distract you". nec or neque continues it: "and let not …".
To tell it from a dependent subjunctive, look at what introduces the clause. If no ut, ne, cum, si, qui, question word or governing verb comes before it, the subjunctive is the main verb and gives an order.