You could do this at home at your own pace. Take a class. Go to the theater, concerts, movies, ball games, or schedule lunch with friends. These also can contribute to memory or thinking problems. Many neurologic and systemic illnesses cause cognitive loss that might be prevented through treatment.
Poor diet can impair mental efficiency.
Take care of yourself. Seek adequate medical care when you need it. Sometimes drugs act in combination to produce more side effects than any of them would alone. Check with your doctor. If you abuse alcohol or drugs of any kind, your thinking may be clouded.