The reason why you lost is becasue he out-teched you. Here read this one:
http://forums.stickpage.com/showthread.php?49448-The-True-Potential-of-Stick-Wars-And-Micro-Macro-Management-(Replay-included)
The main point being, once both players economy are high enough, lower tiered units(such as archers/speartons/etc.) become less viable. You were spending to much money on your archers. Sure you may have been harassing his economy but obviously the damage was not enough to stop his giants.
Something important for you to realize:
1.Archer is 350g.
2.4archers is 1400g.
3.that is 100g short of a giant.
4.I am willing to bet you had more than 4 archers in the very late game.
5.Mid-to late game means teching to higher tiered units, not wasting gold on lower tiered units.
If you're telling me he had the gold income and the army to be able to hide 3-4 giants in his base WITHOUT using them to defend your "harass" your harass was obviously nothing but a small nusiance to him(and your harass sucked, to put it simply).
Also. This game was probably in the very very very late stages seeing as how he had the time to make that many giants. And you're telling me you didn't even bother to tech to giants yourself? What were you spending your better economy(opponent should not have been able to mine 2nd row gold succesfully+you have tower) on? A bunch of low tech units? That is why you lost.
Plus seeing as how you just got back, you're really rusty and you're probably still adapting to the patch. :)