all humans will feel happiness and sadness. yes indeed this is life. God always gives choices to humans. true or false. evil or good, and so on. it's up to you to choose which way. so too when you are having problems. don't let yourself be drawn into sadness.
maybe you are losing someone you love. yes indeed you will feel sadness, and that's a natural thing. but do not drag on sadness. all humans have their own age limits. all are different. you must rise up in sadness.
remember sadness will make your life a mess.