I lack energy
Here are a few areas you can start with if you miss energy:
Diet and exercise
Change your diet, get the input of vitamins you need: more fruit, vegetables. Get rid of junk food. Exercise regularly, move your body, get fit.
Is something draining you?
Check your relationship with people in your life. Establish clearer boundaries whenever needed to protect your personal and mind space. Is anyone in your environment draining you? Work, family, friends?
Emotional fuel, excitement, motivation
Check you daily activities? Are you excited about your day? Focus first on what truly thrills you. What are the activities you find exciting? Make them priority number one. Focus first on what is fun and exciting.