When you are young(20s and 30s), do you invest 100% money into equities, except emergency fund?

How do you overcome the physiological stress of market fluctuations, which would affect almost all of your savings. (Except EF of ~6 months)

For short term goal, i understand we can set aside some of the money into cash equivalent accounts. What if you have a mid-term goal? Like buying a house in 10 years, but not near future? Do you still invest rest of your paycheck into stock market?