If this was just a regular command, wouldn't HaShem just say, שלח אנשים ויתרו? Why say specifically, שלח לך? Rashi answers this famous question with a well known answer.
(ב) שלח לך. לְדַעְתְּךָ, אֲנִי אֵינִי מְצַוֶּה לְךָ, אִם תִּרְצֶה שְׁלַח;, אָמַר, אָמַרְתִּי לָהֶם שֶׁהִיא טוֹבָה, שֶׁנֶּאֱמַר "אַעֲלֶה אֶתְכֶם מֵעֳנִי מִצְרַיִם" וְגוֹ' (שמות ג'), חַיֵּיהֶם שֶׁאֲנִי נוֹתֵן לָהֶם מָקוֹם לִטְעוֹת בְּדִבְרֵי מְרַגְּלִים, לְמַעַן לֹא יִירָשׁוּהָ (תנחומא):
(2) שלח לך SEND THEE (more lit., for thyself) — i.e. according to your own judgement: I do not command you, but if you wish to do so send them.
This scenario reminds me of another scene that plays out a lot of times between parents and children. Imagine this: a young child wants a new toy, an old looking doll- except he just got one, a toy that was even better than this. He just got a new Lego set! His mother says no, but he begs and begs until she finally relents and lets him get the toy, exasperated- didn't he believe her when she told him that he would enjoy the Legos more?
This is essentially what happens in this week's parsha. Bnai Yisrael wanted to send spies to Eretz Yisrael, nervous and afraid of what they would find. Exasperated, HaShem tells Moshe, as Rashi brings down, "I told them it was good when I told them I was going to take them out of Egypt! Now they want to send spies? I'm going to enable them to mess it up."
This encapsulates the idea of what חז"ל tell us, "בדרך שאדם רוצה לילך בה, מוליכין אותו" "On the path that a person wants to go, HaShem enables them." Similar to a parent that gives in to their child's begging, knowing that the new toy isn't as good for them, HaShem gave in to Bnai Yisrael's request, knowing that this would lead to the sin of the Meraglim.
This is true with us. There are times when we think we know what we want, what is good for us, without knowing the full picture. As the age-old mashal states, we are looking at the knotted, misshapen, back of the tapestry while HaShem gazes at the front.
I saw a quote the other day paraphrased from Rav Avigdor Miller, saying that when we daven, we should trust that HaShem is listening to us and will do what is best for us, instead of what we think is best.
I'd like to bring in one more story to really drive this point home because it is so important. I heard a shiur last year from Rabbi Aryeh Cohen, where he spoke about an idea from the Degel Machaneh Ephraim, about what Dovid HaMelech says in Tehillim, 27:4 "אחת שאלתי מאת ה' אותה אבקש" and the strange wording. Why say “I have one request from HaShem, that is what I’m asking for”? The reason for the two types of bakashos is because what Dovid was really saying is, "I only have one request, that which I should be asking for," meaning what Dovid HaMelech would be asking for if he knew what was best for him. That right there is real, practical advice on how to daven and live our lives. We all want the best for ourselves- and that is what HaShem wants to give us.
So often in life we think we know what is best for us, but we don't. Having bitachon in HaKadosh Baruch Hu doesn't mean, "I trust that HaShem will do what I want because he’s good," it means, "I trust that HaShem will do what HE wants, because that's what is good!" That should be our mindset, because ultimately HaShem is our parent and will give in to us if we really want something- even if it's not good for us, just like with the spies.
So trust in HaShem, hand over the wheel, and sit back, relax, and enjoy the ride.