Hiya! You aren't a bad tama mama, you just need practice I promise!
Here is Dez's quick guide to being a vintage tama MASTER.
Three big things -
1 .Keep both hunger and happy hearts filled all the time, if you can! Check stats like clockwork!
2. Keep the weight down by playing games and try to NEVER feed snacks.
3. LISTEN to your tama to make sure you scold it when it calls to you and doesn't need anything.
If I remember correctly, your tamagotchi as an adult (Let's use mametchi or mimitchi as an example, some tamas will be different weights at adulthood) should be 30 pounds all the time because it's the healthiest weight. How do you keep the weight down, you ask? PLAY GAMES! That will take away 1 pound of weight from your tama PER GAME even if you don't win the game. However, you HAVE to win for your tama to also gain a heart from the game. You can also tell what the proper goal weight of your current tama's life stage by playing the game and continuously checking the stats. If the weight stays the SAME number after you play another game or two, THAT is the weight they should be!
Best advice is that a meal will give one heart of "hunger" and the snack will give one point of "happy" in case you are in a hurry. However, it is best to try to NEVER use snacks, they raise the WEIGHT of your tama which is so important.
Your main goal is to keep your tamagotchi at 4 hearts of happy and hunger all the time and have to be kept at a healthy weight. Also, if you keep your tama closeby, sometimes they will call and make a beeping sound even if they don't need anything. This is when you need to discipline them. (You will tell if they either A: need something, like a heart of hunger or happy or B: They need to be disciplined) by seeing if the button on the bottom right that looks like two faces is lit or not. If you can obviously see your tama didn't need anything but that faces icon is still lit, you gotta discipline them.
If you need more info on something, please please ask! But I think this will help!