Give a Little to Gain a Lot
Black to play.
It is a territory versus influence game here. Where should black play next? Think of reasons, don't just use your intuition. Also, think a few moves ahead.
Dia 1
Black has to play in the upper-left corner, more exactly around the place where both black and White's long lines of stones end, in order to complete his wall.
The most natural move isn't always good enough, though: if black just extends with 1 in Dia 2, white plays around 2 on the upper side and Black's influence doesn't look so effective.
Black can do much better.
Dia 2
Dia 3 shows a common sacrifice technique that black can apply here, in order to complete his wall in sente, so he can play first on the upper side.
Black gives away some territory compared to Dia 2, but since the upper-left corner was open anyway, that is a small price to play in this case.
Dia 3
Conclusion
- Playing natural, solid moves is a great skill, but always look out for opportunities - sometimes we can do even better.
- Learn to sacrifice a little in order to gain more.