I'd argue that smoking cessation is important right off the bat to prevent your first heart attack or stroke or cancer.
If you think you are having a heart attack, tell someone or call emergency services yourself. You may think you may be having one bt it could be a myriad of other things that are also bad such as a pulmonary embolus, pneumothoriax, or aortic catastrophy. Your history physical and diagnostic testing help us professionals make the right diagnosis.... even if it's just a muscle spasm or GERD. Seek attention immediately if you are concerned about a heart attack... just don't be too upset when after an hour or two a physician tells that everyone is OK for now.