I was on beta blockers for two years and it did affect me when I stopped them, so I was gradually 'weened' off. However, you would notice a difference after 24 hours when you usually top up your body with the drug. The usual symptoms are stronger angina, such as increased shortness of breath, mild chest pains etc. I found it harder to breathe and it's hardly surprising taking into account that my body was used to this drug for 2 years. Weening off gently allowed my body to adapt rather than shocking it into having a more reactive and powerful circulatory system. If you haven't noticed anything by now, I doubt if you will. Nothing serious will happen, it's not like lack of the drug will suddenly give you a heart attack or anything so please don't feel anxious.