Where's my stamina?

Stamina /n
the ability to endure much physical or mental strain; great energy and strength

***

Seriously, where's my stamina? Today went to play futsal with few pals... within half an hour, i shouted for substitution...

This is BAD, a RED ALERT for a partial sportsman like me...

Back in Nilai, running all around the pitch for full 90 minutes was not a big deal... but now, i doubt my ability to do so...

So, in order to regain my form... I gonna:
1. Pick up my jogging routine
2. Do more swimming
3. Less junk food (applicable??)
4. Less 打 _ _ (err...)
5. Any other suggestions???

p/s: 我要 fit fit... XD