Hi, and thanks for your medical question on eHealth's Ask a Doctor forum.
A BP of 140/90 at the age of 20 is definitely not good. Either this is essential blood pressure without a cause or there is some cause behind this. A complete lab panel should be done to exclude the causes such as heart disease, liver or kidney problems, electrolyte imbalance or hormonal problems including thyroid problems and diabetes.
Take up yoga, deep breathing exercise, or walking. Music and aerobics are also good stress busters. These may be helpful in keeping you relaxed. The other way to monitor your BP would be a 24 hour holter. This will keep recording your blood pressure while you go about your daily routine.
Since a confirmed diagnosis, treatment and solution cannot be given on net please discuss these possibilities with your doctor once. Hope this helps. Take care!