The thing is we live in a spiritual World whether we like to hear it or not which can cause some people to work much harder than others and still end up achieving nothing.
For your friend who is putting in lot of work and not achieving much, he may have to alter something in his life if he really desires a shift. If it's not a case of lack of money management or not working smart, He may want to draw closer to God to break off any curse he might fighting against.
About the main question, I believe in destiny and everyone destiny is what we decide it to be. As they say, your destiny is in your hand meaning you have a part to part in making things work out in your favor.