In French, the subjunctive mood isn't just used for necessity or obligation. You must also use it after expressions of emotion and feeling, such as being happy, sad, or afraid about what someone else is doing.
Être content que & Avoir peur que
When you express a feeling followed by que (that), the verb for the action you are reacting to must be in the subjunctive.
Use être content que (to be happy that) to react positively, and avoir peur que (to be afraid that) to express your fears. Remember that que becomes qu' before a word starting with a vowel.
As a reminder, to form the subjunctive, take the present tense ils form of the verb, drop the -ent, and add the regular subjunctive endings (-e, -es, -e, -ions, -iez, -ent). Because of this rule, the subjunctive often sounds exactly like the present tense.
Other Emotions
All expressions of emotion follow this exact same rule, including être triste que (to be sad that).
Whether dealing with a regular -ir verb (like finir) or a regular -er verb (like planter), simply attach the subjunctive ending to that present-tense ils stem.
