I actually have trouble getting my heart rate into normal target ranges. I always have. If I run hard enough to get myself fully out of breath after just a mile, I'm still not in "target" range for cardio.147 isn't that high really, its ONLY 147 AS you are OLD, if you were younger 220 is more like the max, so that's 70 bpm down on a 25 yo. Any cardio training should easily get you heart up to 150, the hard part is not getting it higher, not reaching 150
by yourself a heart monitor, go for a,run, see how,scary high your heat rate is,,, stop worrying, throw monitor in bin, get on with life