If I felt 25 I’d feel very young! What’s going on in your life @Zachary_Mendes123? Are you studying hard? Working too many hours in your job? How are your relationships with your family or your partner? Are you eating healthy food? Getting enough sleep? How is your health?
All and any of these things can make you feel tired and burned out. What’s going on to make you feel ‘old’?
When you say you feel old are you talking about your physical aspect or mental. Do you hurt more or do you feel like you are more mature than your peers?
HA! You crack me up! I’m 66 and was my all time strongest when I was 36.
Perhaps your body is telling you that you need a break or more sleep. If you continue to feel down for a long period, then a medical checkup would be a good idea.