Exercise-how much and when post endarterectomy

I had TIA's and had a carotid endarterectomy just over 3 weeks ago. This last week I've managed to do some brisk walks, gradually building time up. I want to start doing yoga at some point and prior to all of this I was doing kettlebell work outs which I want to get back to but know my fitness isn't up to this yet. Is it just a case of listening to my body as to when is the right time? Or is there any guidance around this as neither the hospital or my GP have provided this. 
Many thanks.