conditional forgiveness?

Matthew 6:14-18

For if you forgive others their trespasses, your heavenly father will also forgive you, but if you do not forgive others their trespasses, neither will your father forgive your trespasses.

Is Jesus suddenly suggesting that forgiveness is conditional? What happened to grace?! If I have to forgive to receive forgiveness, then I'm in real trouble. While BW Johnson, might be able to say of this verse: "We ask, in other words, that he may mete out to us what we measure to others" - I wouldn't dare say that to God, I might as well ask him to strike me down!

Let's look at some other commentators:

Gill:

"not that the forgiveness of others is the procuring cause of forgiveness with God, which is the blood of Christ; or of the manifestation and application of it, that is, the advocacy of Christ; nor the moving cause of it, that is, the free grace of God...
... where men are not of a forgiving temper to their fellow creatures and fellow Christians, how can they expect forgiveness at the hands of God? or what sense of pardoning grace can there be upon their minds? Had they any right apprehensions of the grace and goodness of God, in the forgiveness of their sins, this would influence their minds, and engage their hearts to forgive such who have offended them...
... [if you are unforgiving] your Father has not given you a true sense of the pardon of your sins, nor can you be certain that he will; nor have you any reason to expect it"

JFB:

"it will not be thought that our Lord here teaches that our exercise of forgiveness towards our offending fellow men absolutely precedes and is the proper ground of God's forgiveness of us. His whole teaching, indeed--as of all Scripture--is the reverse of this. But as no one can reasonably imagine himself to be the object of divine forgiveness who is deliberately and habitually unforgiving towards his fellow men"

McGarvey & Pendleton:

"[unforgiveness] can only exist in a heart blind as to the amount of its debt

If you are struggling to forgive someone, don't worry. We need God's grace to forgive. You recognise the need to forgive but are finding it hard - cry out to God for him to enable you to forgive as you have been forgiven. If you stubbornly refuse to entertain the thought of forgiving someone - you probably aren't a Christian, you might be blind to the amount of debt you are in with God - ask him to reveal your sin to you, because only when we see the depths of our own sin do we really see the beauty of the gospel