Im scared my dog will die!!!=[?

i have a 6 year old miniature beagle soon to be seven. he is not overweight although he isnt really skinny and his hair is not fading to gray but i can't stop worrying about him! i DON'T want him do die EVER. i want him to have the best life ever. i really don;t know what im going to do without him. it scars me too. all i do is worry about him when i see him. i heard that when you don't brush dog's teeth they can have heart problems? This scars me because i don't brush my teeth and i remember the vet saying something abut plaque a few years ago. Please tell me what you did when you lost your pet and is there anything i can do to stop worrying? thanks=]