Some things to consider:
If you are going to play a forcing exchange (example T13-S16), then come back to defend (example R12), consider omitting the forcing exchange and simply defending. This preserves some of your options (corner aji in this case, in the admittedly unlikely event you later get to invade the corner and peep at S16). It also preserves ko threats. In this particular position, it costs you nothing to wait, since your opponent is never going to play T13 himself (earning just one point in gote). Finally, the forcing move carries a large enough threat that it will remain your privilege (sente) for the forseeable future.
There are contrary cases where you should play a forcing move before defending. In particular, if your "forcing" move is sente now, but may not be sente later, you should take it while you can. This frequently happens when you have a group which needs to live in gote, but you can make a few profitable exchanges before living. Provided your forcing moves actually threaten to live, your opponent will answer them now, in order to force you to eventually live in gote. (Clear?) But if you live in gote first, he may not answer your forcing moves later. That is, the exchanges may no longer be sente for you. The proverb is "kikashi before living".