That's why - you will never get out of your
cycle and periodic mood swing will haunt you and you will never
gain that kind of confidence others have.
What makes life complete; is a question rather subjective and
personal. Even if I don't feel my life is 100% complete, at least I
know I am not lifeless. But how you may say (think I repeated this
before twice, but don't worry man, I am a naggy sort. When the
situation arise, I will repeat without sweat 
)
The psychological feel of lifeless is due to unfulfilling things we
do everyday. It doesn't give us confidence, neither much
satisfaction nor happiness in doing them. Likely, they are social
& personal duties, liabilities or tasks we have to perform. You
do them because have to and don't have much choice. You can do them
less of course: but they can share extra energy on the next
part:
Seek and understand your interest first; your leisure time
(residual time after work) It could be anything, from Origami to
sports. These things are likely to make you feel good, but
confidence only flows in if you are quite expert/good in them (In
your own opinion). It always goes hand in hand - good at something
automatically gives you confidence.
With confidence, you would want to do more of the thingy. In the
process, you get to know people with similiar interest or at least
it may help you in the future. (You can use your skills in Origami
to fold all sorts of lovely dopy thingy for your gf in the future,
for example).
By keeping your mind open and the desire to try new things - you
effectively repeat the process. Keep in mind that these things are
interest which makes you feel happy in doing them - then as time
goes by, you wouldn't feel lifeless because they are things you
want to do on your on
accord. 
P.S: Here's the theory; practical is the part on how you go about
reflecting about your liking and execute the plan like above. With
a vast interest, if also affects your communication skills for the
better - imagine chatting with someone who knows many things than
one who is 'lifeless'. With good communication and confidence comes
Art of Seduction, blar blar blar.... it's a linked cycle.
Knowing is only one thing; attempting is
another.
Cheers
