I'm looking for manga that when u read it, it kinda give u some sort of motivation n courage to do something..for now i've read Denpa Kyoushi, GTO and Naruto..

If the world doesn't have a hero why don't u become one - Denpa Kyoushi.

Sket Dan was a pretty motivating manga, cuz if you think you`re a loner in school or something like that this manga will prove otherwise. Just cause you have a dramatic past or present it will make you remember that you your family and friends will be there for you

Welcome to NHK! (I've only seen the anime though) - it gives you motivation to NOT become like the protagonist (at least it gave me motivation not to drop out of university)

Just a heads up, I was around 12 when I read some of NHK and it just made me feel depressed for a couple of days. Some people love it though (I mentioned my age because it was a long time ago so perhaps i'd feel differently now. I keep planning to go back to it eventually)
Anyways, I realise this is shoujo and you've only listed shounen but, seriously, just give it a try. Cat Street. It's about a girl who's closed herself off from the word and thanks to a coincidence begins to come back out into the world. And it's fantastic. Now let me find a shounen on my list....oh! Beck Is an awesome series about some guys trying to get success as a band.
Slam Dunk - good sports manga probably meet your requirements and this is my favourite, easily.
Rookies is another great one. The drama/man-tears is perhaps overdone here htough
A couple of Seinen:
Team Medical Dragon
Uchuu Kyoudai - A guy trying to go back to his dream and become an astronaut like his younger brother now is
Holyland - a group of damaged people trying to find themselves and a place.

Sakurasou no Pet na Kanojo
Most of the main characters are chasing their dreams.
But most of their dreams are different.
It may appear to be a romance comedy harem ecchi with no substance but the part on chasing dream plays a huge part.

I back Slam Dunk right up- this manga was cited as an influence in the increased popularity of basketball among the Japanese youth during 1990s (via wikipedia) and there was also J. R. Sakuragi, a Japanese-American basketball player so inspired, he named himself after the main character of the manga. Personally, I don't give a shit about sports, being fat and lazy, but after I read SD, I really wanted to try sports.

Harukana Machi-E is pretty good. It's about the chance to relive your youth again, but with all your adult memories intact. It's kinda about the choices and the consequences that follow, so pretty much philosophical if it's your thing. I liked it. Makes you think a lot about your life, and what you should do.

For some reason, I am a Hero was strangely encouraging, it being a slice of life horror manga. It emulates the reality of society and life in a hypothetical zombie situation exactly with a loser protagonist, one that really hits home with his career brimming with so much potential but sadly, unfulfilled. It's how he copes with the damningly bleak situation that really gives you hope.

I'm so gonna check out Welcome to NHK!