When one has reached the age of shidduchim, one should search for ashidduch as if looking for an object one has lost.* One must be proactive in this issue and not just await a suggestion.**
One should not be deterred by any difficulties or disappointments. Indeed there is no cause for depression if things are not working out, rather one should increase in one's simchah*** in doing this mitzvah, for a true match is made in Heaven. One need only make a firm resolve that one will seek to fulfill this mitzvah as any other of the mitzvos. Hashem does not come with unreasonable claims to His creations, and since Hashem has commanded that one perform this mitzvah, then it is entirely possible. One needs to be persistent and conscientious to bring it to fruition.+ Strengthening one's bitachon is in itself a segulah for a shidduch.++
It says that "G-d will bless you in all you do." This means that the blessing of Hashem comes when a person makes an effort -hishtadlus. So too in a shidduch, a person must make all the necessary efforts and hishtadlus in the natural manner to find a shidduch.+++
* This expression of Chazal (Kiddushin 2b, Niddah 31b) is not just fanciful writing, rather it suggests that without a shidduch one is actually missing something, as Chazal say that one who lives without a wife is without joy - Igros Kodesh Vol. 12 p. 195.
** Igros Kodesh Vol. 18 p. 436. Just as when one loses any item one proactively searches for the lost object, and does not wait for someone to come and say they found it, so too must one be proactive in looking for a shidduch -- Igros Kodesh Vol. 6 p. 144, p. 178.
*** Igros Kodesh Vol. 10 p. 259.
+ See Igros Kodesh Vol 7 p. 190. Rabbi Zusia of Anipoli learned a number of things from the conduct of a thief. One thing he learned was that even if he was not successful the first time, he doesn't give up and will try a second and third time. Similarly with shidduchim, one should try and try again and in the end one will find something. One should not be deterred by the difficulties -Igros Kodesh Vol. 5 p. 119.
++ Igros Kodesh Vol. 19 p. 427, Vol. 10 p. 259. In reference to shidduchim, Chazal use the reference, "It is difficult to put them both together as it was to split the Red Sea." The analogy may be taken further: just as the splitting of the Red Sea came about through strength of faith and trust in Hashem, so too a shidduch will come about through strengthened Bitachon - Igros Kodesh Vol. 8 p. 219.
+++ Igros Kodesh Vol. 5 p. 119. Vol. 16, p. 327. In fact, the mere making of a "Keli" ( a vessel) draws down results, and therefore if a person is not finding a shidduch it could be that they are not putting in the necessaryhishtadlus in searching for one, rather they are just going through the motions "to fulfill their duty" and not with the requisite energy as in searching for a lost item - see Igros Kodesh Vol. 10 p. 354. In one letter the Rebbe berates someone for not putting in enough of an effort to find a shidduch but them finishes the letter with a blessing that since a shidduch is something that transcends nature, then even if naturally not enough hishtadlus is being made, nevertheless the shidduch should come about in a supernatural way! - Igros Kodesh Vol. 14 p. 345.
One should not be deterred by any difficulties or disappointments. Indeed there is no cause for depression if things are not working out, rather one should increase in one's simchah*** in doing this mitzvah, for a true match is made in Heaven. One need only make a firm resolve that one will seek to fulfill this mitzvah as any other of the mitzvos. Hashem does not come with unreasonable claims to His creations, and since Hashem has commanded that one perform this mitzvah, then it is entirely possible. One needs to be persistent and conscientious to bring it to fruition.+ Strengthening one's bitachon is in itself a segulah for a shidduch.++
It says that "G-d will bless you in all you do." This means that the blessing of Hashem comes when a person makes an effort -hishtadlus. So too in a shidduch, a person must make all the necessary efforts and hishtadlus in the natural manner to find a shidduch.+++
* This expression of Chazal (Kiddushin 2b, Niddah 31b) is not just fanciful writing, rather it suggests that without a shidduch one is actually missing something, as Chazal say that one who lives without a wife is without joy - Igros Kodesh Vol. 12 p. 195.
** Igros Kodesh Vol. 18 p. 436. Just as when one loses any item one proactively searches for the lost object, and does not wait for someone to come and say they found it, so too must one be proactive in looking for a shidduch -- Igros Kodesh Vol. 6 p. 144, p. 178.
*** Igros Kodesh Vol. 10 p. 259.
+ See Igros Kodesh Vol 7 p. 190. Rabbi Zusia of Anipoli learned a number of things from the conduct of a thief. One thing he learned was that even if he was not successful the first time, he doesn't give up and will try a second and third time. Similarly with shidduchim, one should try and try again and in the end one will find something. One should not be deterred by the difficulties -Igros Kodesh Vol. 5 p. 119.
++ Igros Kodesh Vol. 19 p. 427, Vol. 10 p. 259. In reference to shidduchim, Chazal use the reference, "It is difficult to put them both together as it was to split the Red Sea." The analogy may be taken further: just as the splitting of the Red Sea came about through strength of faith and trust in Hashem, so too a shidduch will come about through strengthened Bitachon - Igros Kodesh Vol. 8 p. 219.
+++ Igros Kodesh Vol. 5 p. 119. Vol. 16, p. 327. In fact, the mere making of a "Keli" ( a vessel) draws down results, and therefore if a person is not finding a shidduch it could be that they are not putting in the necessaryhishtadlus in searching for one, rather they are just going through the motions "to fulfill their duty" and not with the requisite energy as in searching for a lost item - see Igros Kodesh Vol. 10 p. 354. In one letter the Rebbe berates someone for not putting in enough of an effort to find a shidduch but them finishes the letter with a blessing that since a shidduch is something that transcends nature, then even if naturally not enough hishtadlus is being made, nevertheless the shidduch should come about in a supernatural way! - Igros Kodesh Vol. 14 p. 345.