I wouldn't say it's "normal" for your heart rate to go to 150 BPM on 50 mcg. of clenbuterol. I've been up to almost 3x that much and my resting heart rate didn't crack 90. It's been a long time since I've used clenbuterol but that isn't because I think its terrible like everybody else in this thread seems to think. 150 BPM is high but your max heart rate is probably well over 180 so it isn't going to do any damage in my opinion.
It is true to a point that everyone is different regarding how different substances affect them, but I wouldn't call you an idiot for starting with 50 mcg. per day, it isn't all that much. Also, the half life of clenbuterol is 36 hours or so, which means that after 36 hours half of it is inactive, 36 hours after than it's down to 25%, and so on. So, although you may be uncomfortable now, you'll be ok and probably will feel a lot more normal tomorrow. I suspect it isn't just the clenbuterol that has your HR at 150, I think it's anxiety also. Chill bro, you'll be ok.