At 18 years old you are a man, with the responsibilities of a man. You'd think I might have some wisdom for you as you reach this age. You'd be right. Here's the short version.
There is no substitute for truth and honesty. Without truth there is only illusion.
You cannot control your life. You can and should control your actions in life. Do so with wisdom and compassion.
Be tolerant of the faults of others, for we each are faulty. Never be tolerant of wrongdoing. As Edmund Burke said "All this is required for evil to triumph is for men of good will to do nothing." Evil cannot and should not be tolerated.
Always be truthful. Always be kind. Never quit.
God does not promise you happiness - but He requires obedience. Be disobedient at your peril.
Micah 6:8 - "He has shown you, O man, what is good; And what does the Lord require of you but to do justly, to love mercy and to walk humbly with your God."