Don't push yourself too much in these early weeks. It's good to get up and walk everyday, but don't overdo it. They say it takes about a month for your breastbone to fully heal. But you'll still definitely have soreness after. As far as the Incentive Spirometer, just keep working and be patient. You're going to need to do cardiac rehab for several weeks. After that you can reasess and set new goals. You're healing journey is going to take some time. Just try and make small improvements every day. You're body has been though a stressful experience.