Birthdays always feel like big milestones, but there's something about the transition from your 30s to 40 that feels especially major. The big 4-0 can make you feel both older and wiser.

Britney Spears is celebrating her 40th birthday ... for all the b-day wishes 拾 !!!! Psss I didn't even drink the champagne 壟 no lie !!!!" Spears accompanied her message with a video ...