what do you mean by heart? Heart as in you get up when you're knocked down or heart as in cardiovascular fitness?

Heart in the figurative sense isn't something you learn, in my opinion. you're born with it, you're either a fighter or your not. I could go on and on about how American society in this day and age is seriously lacking HEART!!!! as a firefighter, a (relatively new but extremely eager) boxer, a former all-league football player/captain, wrestler and coming from a blue-collar family, it makes me sick!

If you want heart, get on youtube and watch Arturo Gatti fight Irish Mickey Ward. that's heart, my friend. heart is when joe frazier told muhammad ali, "WELL THEY TOLD YA WRONG, PRETTY BOY!"

heart is getting out of bed in the morning and right away dropping to the floor and doing 50 pushups, because thats 50 MORE than the other punk is doing!!!!

ok, sorry, I'm good now.

you really do need to get into a gym and have a trainer teach you. otherwise you'll never really have proper technique. a trainer will also show you how to defend yourself.

if and when you get into a gym, after you get all your paperwork squared away you'll start sparring. that's when you really learn defense, because you'll either keep your gloves up and block those shots or get tagged time and time again.

alright, so this is more the opinion of myself and my coaches.
the speed bag isn't necessarily to develop hand speed. it's more for developing stamina and strength in the shoulders and arms so you can throw combinations harder for longer periods of time. Ive seen guys in my gym throwing hooks and combinations at it, but I dont see the point when you can just do that on a heavy bag.

for your stamina... the absolute best way is to get a good pair of running shoes and run yo butt off. I run six days a week, mon, wed, friday are 3 mile days and I do "interval training" on tue, thurs, and saturday. sunday was set aside by God for boxers to rest.