I cannot promise you a lifetime or even a day,
For my days and yours are bound to others through a life time commitment.
What I can offer is simply ...me.
For whatever amount of time we can steal.
I offer you laughter for laughter is beauty.
I offer you honesty as honesty is pure.
I offer you patience as patience is needed to gain trust.
I offer sincerity for through my sincerity I will show you my inner being and desires...
All I ask in return is for you to be honest and open
for through your honesty and openness I will receive from you all that I offer.
It's not great, but it has a lot of promise. Your use of repetition of "I offer you", for example, is good, but there really isn't any kind of rhythm. Try reading it out loud and breaking up the lines so that it reads more slowly and highlights your most important ideas.
If I were editing this as my own poem, for instance, I would break it up:
I cannot promise you a lifetime
or even a day,
For my days and yours are bound
to others through a lifetime
I think when you do that you'll see some places where rearranging your language would improve it, but overall I think your poem just needs a facelift. Keep on writing!