(a)

I have thought that prayer is for us to recognize what we get from

HaShem and what we lack.

Prayer, according to the Gemara in Berachos (34a), is actually comprises three purposes. (1) Praise of G-d (which describes to us, in terms that we understand, a little about Who G-d is); (2) Our needs and desires; (3) Our acknowledgement and gratitude to G-d for giving us everything that He gives us (life, health, sustenance, etc.). This third part is what you refer to as recognizing "what he get from Hash-m."

You may notice that the three parts of the Shemoneh Esrei (that is, (1) the first three blessings, (2) the middle 13 blessings, (3) the last three blessings) are the three parts of prayer that we mentioned above.

Your question focuses on the second part of prayer, that of our requests.

(b)

If we can cause HaShem to "give" us something through prayer,

are we not falsely setting ourselves up as too powerful. Are we not

actually manipulating HaShem?

When my child asks me for something, such as a cookie, I have two basic options. I can either give him the cookie, or not give him the cookie. To give him or not to give him the cookie is my choice. If I decide to give him the cookie, does that mean that my child is in control of me? Is my child that powerful? Of course not. I gave him the cookie because he was a very good boy and because I love him. (Even when I don't give him the cookie, I still love him. In fact, sometimes my not giving him the cookie is a result of my love for him -- I want him to be healthy and not get ill from the cookie, for example.)

Hash-m has free will to grant us what we pray for. We do not "cause" Hash-m to give us anything. It is His choice. Sometimes, He decides not to give us what we ask for, and sometimes, he decides to give us what we ask for. We strive to be better people so that G-d will be more inclined, so to speak, to decide to grant us our desires. Hash-m is the One with the power to decide whether or not to give us what we ask for.

Of course, you are correct that Hash-m did give us the opportunity to pray for things that we want, and as a result of our dedicated and sincere prayer, He will give them to us. But this is merely another example of His power, not ours. This is the way He set up the world, so that man would realize that he depends on G-d for everything.

I hope this was helpful. Take good care,

Yisroel Shaw