Originally Posted by m0b00st
Actually the jungler is meant to be a player who can intermediate between all lanes and help lanes out when the opportunity arises, not babysit a lane because they are making bad decisions or getting outplayed. If they are babysitting a lane, they might as well be in the lane permanently as opposed to jungling.
As jungle Amumu in the last solo queue I played I went 8/10/31 because I jumped in to initiate, I built to be a secondary ap carry/tank using a build that I designed that worked, I placed wards for all my lanes when theirs ran out, saved carries from ganks by counter-ganking when they overextended to chase, and overall supported the team.
You have to find the champions that reflect your play style and practice with them in draft mode by yourself or with a friend.
I am good with a lot of the champs, bad with others, but I am great with these 18;
Lee Sin (Jungle)
Try these champions out and see what happens, maybe they'll click for you like they did for me.