Guys can and do fall in love. They may have been the wildest and the craziest in their youth but when they meet the right woman they will fall in love even hopelessly, settle down, and probably become more faithful and loyal than most.
You will know when a man is really in love with you because although we are always being told that men are so different to us women, when it comes to feelings and emotions we are all human whatever sex we are and we want to love and be loved.
You will notice how he he can't wait to hold you, can't wait to see you and when he is with you he is just happy to be with you and not just for the sex.
As for giving your heart away, well the saying 'no risk - no gain', has to apply here, you have to risk it if you wan't to fall in love with someone. And after all, most things in life are a risk but I think you will find that your inner instinct will tell you whether the man you think you have fallen for warrants you giving all your heart to him or not, and if it tells you that he is the right man then don't hold back because then you would be depriving yourself of some of the beauty of falling in love.
And if, unfortunately you make a mistake, and this wasn't the right man for you, well don't despair. You have learnt a lesson, you will get over it, you will have learnt how to judge men a little better and the next time an eligible man comes your way you will be that wiser.
I am quite a bit older now. I made a very big mistake when I was younger by choosing the wrong man but now at my age I think I at last can differentiate between a good and genuine man and a suave girl pulling one!