Great question!
I wish I had an answer, but each of my decades so far has been split between highs and lows - would be easier to split into half decades.
0-5 great
5-10 my mum goes off kids when they stop being very little and cute 
10-15 meh, as they are for most adolescents
15-20 very social, lots of fun
20-25 uni, with bad depression
25-30 mostly living abroad having a good time
30-35 difficult time - single, fat, thought I'd never have kids
35-40 lost weight, fell in love, marriage, babies 

40-45 illness for me, bereaved, marriage problems
45-50 moved to forever home by the sea, career upturn, creative inspiration, marriage and health improved.
Hoping for good things from my 50s, but prepared for a game of two halves!