Actually, think about it this way : Let's say you're destined to
marry your 5th boyfriend, ok?
So first boyfriend, you fall in love and give it your all, 100%, no
holds barred. Then, you break up. You are devastated,
naturally.
On to Boyfriend #2. You think back to the pain you felt the first
time so this time, you 'discount' 10% and give it only 90% in the
relationship. Things fall apart. On to the next.
This is Boyfriend #3. Fresh from two bad experiences, you decide,
this time, you keep 20% to yourself. Time flies, differences
surface, promises are broken.
Now, it's #4. You get so frustrated from all the heartbreak and you
want to protect yourself this time so you're holding back 30%. You
never want to get your heart broken so badly again. Whaddaya know,
it again doesn't last and ...
Finally, THE one, Boyfriend #5. He's THE one you're destined to be
with. BUT, he feels that you're holding back and indeed you are!
You've been so heartbroken before and you're so scared of all the
pain and broken dreams and promises that this time, you're holding
back a grand 45%! Poor guy... he has done nothing wrong but
already, you're giving him the suspicious eye and don't even want
to entrust him with your heart. So you cheat yourself and him of
what could've been an awesome, loving and trusting relationship
just because of your previous hurts. This poor chap is paying the
price for all the previous boyfriends who broke your heart.

Think about it... fair or not? 
The temptation is to hold back when you meet someone you're falling
in love with but you're not sure if he feels the same. Unrequited
love is truly heartbreaking and so frustrating. I feel tempted to
hold back myself, when I meet someone I adore. However, I always
remind myself of this analogy and tell myself that it's not fair to
cheat him and me of a potentially great relationship, then I let go
of my fears as best as I can and just enjoy his company and then
maybe, just maybe, he'll bask in the 100% I give into the
relationship and we'll end up going through life's journeys
hand-in-hand and heart-to-heart. 
OK, a little dramatic... but I hope you're getting the gist of my
post.
Holding back does
no one any good. What's the worse that could happen? Rejection. So,
ok, pick yourself up and move on. Pai seh only lasts a day or
two... regret lasts forever. 
Good luck in love, Ladies! I need it myself! hehehe! 