Help comes in many different forms. To bolster something is "to add to, support, or uphold" that thing. The verb comes from the noun bolster, a cushion or pillow. The idea of cushioning, propping up, or giving a boost is central to the verb. However, while this noun bolster is most likely to prop up a person, the verb bolster is more commonly found in discussion of concepts and ideas. For example, you might bolster a case or an argument, or bolster a friend's confidence. Similarly, internet companies will seek to bolster their traffic, and government agencies strive to bolster the economy.
The most general feeling of sorrow or unhappiness can be captured with the adjective sad. The word bitter, on the other hand, describes a more pointed feeling, often one of disappointment, sharpened by resentment, hostility, or cynicism. A bitter sorrow is one that is deeply grievous or hard to bear. A bitter lesson is one that is hard to accept. And bitter rivals are competitors whose relationship is marked by intense antagonism or hostility. In all of these, you can find traces of bitter's earliest sense in English: "having a harsh or disagreeable taste."
To be jubilant is to show great joy or triumph. Contrasted with the word happy, which conveys delight but not necessarily to a high (or noisy) degree, jubilant shouts its elation from the rooftops. It comes from the Latin verb jūbilāre meaning "to shout, whoop," and fittingly, you're most likely to find it describing the mood or manner of people gathered in celebration, or with something to "whoop" about, as a success or victory.