Feelings and character

The simple rule "doubt → subjunctive" does not cover this, because a feeling triggers the subjunctive even when nothing is in doubt:

Je suis content que tu sois là. — you are definitely there

The reason is that in this sentence, your being there is not the news — it is taken as given. The news is that I am pleased.

The subjunctive marks exactly that: this clause is not what I am asserting.

The feelings that take it:

And one exception: espérer que takes the indicative.

J'espère qu'il viendra. — not vienne

This exception is easy for you and the rule is not. English says "I hope he comes" with a plain indicative, exactly like French — so espérer que … viendra needs no effort at all.

The work is everywhere else. English also says "I'm glad you're here", "I'm sorry he's ill", "I'm afraid it's late" — all indicative, all requiring the subjunctive in French. There is nothing in the English sentence to warn you, which is why this has to be learnt as a list rather than felt.

The shortcut that avoids the whole problem: when both halves share a subject, use an infinitive instead.

Je suis content d'être là. — rather than que je sois là

And that construction is the natural one in French anyway, so it is not a dodge.